1stForge

STL Files, mostly for fantasy battle, but at least one compatible with Epic.

AdmGR Projects Yard

A selection of smallscale ships compatible with Imperial and Necron forces.

alexgor248

A number of great-looking STL files compatible with Imperial Forces

Alternative Armies

Mostly caters for larger scales but there's a good selection of 6mm miniatures and terrain.

AndgrimnerDesigns

STLs Compatible with Ork, Chaos, and other forces.

Ankylo Miniatures

STL Files, some compatible with Epic. Runs Kickstarter campaigns that are often relevant to Epic.

Artisans_of_Vaul

STL Files compatible with Imperial and Chaos titans

AsmodeusLord

STL Files compatible with Epic including several Nurgle units.

BattleBlingStore

A large selection of Titan weapons and accessories, as well as products compatible with other systems.

Battlefleet Galaxy

Finely detailed starships compatible with Imperial and Chaos forces.

Bishok

STL Files compatible with Orks and Imperial, including Titans. Also a large selection of terrain.

BitGloomMinis

STL Files, compatible with specific Imperial Guard regiments.

Bits Blitz (CULTS)

A large selection of smallscale terrain, fun accessories and miniature STLs.

Bits Blitz (Shapeways)

Starships compatible with Imperial forces.

Bluesquat

A selection of starships, some of which could be used for Imperial and Ork forces.

Brigade Models

I wide variety of smaller scale models, including some suitable for Epic.

Brother Arminius Miniatures

Some lovely-looking STL files, compatible with Imperial, Chaos and Necron forces.

Chaostemple Miniatures

Models compatible with Guard, Necron, and other forces.

Charliebot

STL Files, some compatible with Epic.

Doom Pig Miniatures

A couple of very nice Tzeentch compatible miniatures.

eBay

Plenty of original GW models, many reassuringly overpriced.

Edge Miniatures

STLs, Mostly for larger scales but there are some lovely aircraft compatible with Dark Eldar forces.

Eureka Miniatures

Mostly fantasy miniatures, but there are a few that could be used for Epic.

Facebook Buy Swap & Sell

Make a trade and post a picture of your breakfast / cat / current vista at the same time.

Fantasy Cult Miniatures

Larger scale miniatures, but one would make an excellent Dark Eldar Titan.

Fusion Shipyards

Spaceship STL files compatible with Imperial and Squat factions.

Gregster's Lab

Most of Gregster's models can be found on Vanguard Miniatures, but there's at least one good Squat proxy here.

Grim Dark Bits

A selection of starships and other models compatible with Imperial and other forces.

Grimdark Terrain

Mostly terrain (obviously), but also a few models suitable for use as proxies.

HLS Models

Purchased the Steel Crown Productions line, but don't seem to be restocking models.

Italianmoose

Starships compatible with Imperial, Eldar and Chaos forces. Also sells via Vanguard Miniatures.

Jazzmantis

Lots of retro style models, some compatible with Ork armies.

JimmyZimms

Tropical dwelling hobbit who offers STLs compatible with Imperial and Chaos forces.

Khurasan Miniatures

A good range of models compatible with a variety of forces. MiniWars currently has an incomplete listing.

King Games

Not specific to Epic or 6mm, but a couple of models are compatible with Chaos forces.

KMFP Designs

An expansive range of STL files compatible with Space Marines, Mechanicus, Squats and more.

Knightmare Miniatures

Miniatures for larger scales, but one would make a good Lord of Change.

Lord_Chronos

Some of the finest Space Elf themed STLs to be found.

Magister Militum

Mostly not intended to be Epic compatible, but a couple of miniatures would fit.

MegaSonicPunch

Easily the best supplier name listed. Supplies printed Grimdark Terrain models.

Mewiththeface

Several STL files compatible with Tyranid and Necron forces.

Microworld Games

Models that are compatible with a variety of forces, most importantly, Eldar Exodites!

Miffles_Makes

STL Files compatible with Adeptus Mechanicus forces.

Mighty Minis UK

Supplier of models and terrain from various STL designers. Custom 3D printing also available.

Mkhand_Industries

A large selection of STL files, many compatible with Epic.

National Cheese Emporium (CGTrader)

STLs Compatible with Space Marines, Necrons, and more.

National Cheese Emporium (CULTS)

STLs Compatible with Space Marines, Necrons, and more.

National Cheese Emporium (Shapeways)

Models compatible with Space Marines, Necrons, and more.

nofixedforge

Starship STLs compatible with Imperial, Chaos, Necron, and other forces.

Nuclear Shrimp Games

Models compatible with Imperial and Ork forces. Unclear whether the company is still running.

Onslaught Miniatures

A large selection of models compatible with Imperial, Chaos, Dark Eldar, Squat, and other forces.

Phoenix Forge

Starships compatible with Tau, Eldar, Necron, and other forces.

Privateer Press

Larger scale models, but a few would make good Dark Eldar Titans.

RealmOf3dprints

Supplier of printed models from various designers. Compatible with Space Marines, Orks, and others.

Reaper Miniatures

Models for larger scales, but a couple would make good Chaos Daemons.

Rebel Minis

Models for other scales, but a couple would make good Chaos Mutants.

Red Nebular

Plenty of fun retro models, many suitable for use as Epic Orks and Gargants

RicktheBarber

STL Files compatible with Imperial and Chaos factions.

Scourge Scenics

A large selection of printed models compatible with Imperial, Chaos, and Ork forces.

Shrike Studio

A small selection of STL files, at least one would make a good titan.

Splintered Light Miniatures

Models for other scales, but some would make good Chaos Mutants.

Strato Minis

More futuristic than grimdark, but some of the models are compatible with Epic forces.

Studio DR

Not specifically for Epic or small scales, but there are few good Chaos Titan proxies.

Sulejman49

STL Files compatible with Imperial and Eldar forces.

Tabletop Art

For larger scales, but they have a good Necron Nightbringer proxy.

Tactical Command Forum

The original Epic community site. Much has moved to Discord or Facebook, but you might still find gems here.

TDoesEpic

STLs Compatible with Dark Eldar and other forces.

Tordo Miniatures

Plenty of STLs compatible with Imperial and Chaos forces. Generally 8mm scale but would reduce down to 6mm if required.

TTCombat

Supplier of Dropzone Commander models, some of which would be suitable Epic proxies.

Vanguard Miniatures

A huge range of miniatures compatible with Space Marine, Guard, Ork, Eldar, Chaos at 6-8mm scale and also plenty at 3mm.

Wakes Emporium (Gumroad)

Highly detailed STLs compatible with Orks, Imperial, Tau, and other forces.

Winter's Bioforge

Finely detailed hand sculpted models compatible with Tyranid forces.

Zepeda 3D

3D Artist who does not specialise in gaming miniatures, but does offer a perfect Chaos bomber.