What follows is a gallery of game development editor screenshots that I have collected over the years. This is by no means an exhaustive collection but one that I hope will help you find inspiration.
If you wish to contribute editor images from your own collection, feel free to email me at jovan@gamedevs.org or drop in the IRC channel #gamedev on AfterNET.
You may also be interested in GameDevs.org for a collection of technical publications relating to game development.
Offset Model Editor
Model Editor for Project Offset
Age of Wonders Map Editor
Unknown Map Editor 1
Unknown Map Editor 2
Dungeon Siege Editor
Dungeon Siege Editor
Shadowrun
Fallout
Age of Wonders Map Editor
Shadowrun
Warcraft 3
Crysis
Wakfu Map Editor
Wakfu Map Editor
Wakfu Map Editor
Wakfu Map Editor
Wakfu Map Editor
Shadowrun
Heroes of Might & Magic 3
Final Alert (Red Alert)
Diablo 2 (Unofficial)
Age of Empires 2
FrostEd
Stronghold
FrostEd
FrostEd
UnrealEd 3
Fallout: BoS
Color-coded collision volume and event triggers.
Wakfu Map Editor
Object picker
Breakout
Breakout
Voxel Editor (Voxie)
Age of Empires 2
Modeling and animations for Age of Empires 2 was all done inside of 3ds Max. Afterwards, it was exported as a series of animated frames.
Cossacks
Cossacks
Neo Geo Sprite Editor
Neo Geo
Neo Geo Sprite Editor
Neo Geo
Neo Geo Sprite Editor
Neo Geo
Neo Geo Sprite Editor
Neo Geo
Conan: Lost Temple
Genesis
Riptide GP Editor
Riptide GP
Vision Game Engine vForge
Starcraft II
Destiny Tag Editor (Bonobo)
Destiny Content Explorer
Destiny Shader Preview
Destiny Content Preview (Mantini)
Halo: CE Sapien
Object/AI placement. Levels/Models are designed in 3DS Max
Halo CE: Guerilla
The editor for all tags in the Halo (Blam!) Engine
Halo 2 Guerilla
Halo 2 Sapien
Sphinx and the Cursed Mummy
Animation editor
Sphinx and the Cursed Mummy
Map editor
Sphinx and the Cursed Mummy
Script editor
Sphinx and the Cursed Mummy
Map editor
Dying Light
NavMesh builder
Dying Light
NavMesh preview
Dying Light
NavMesh AI
MT Framework 1.1
Capcom's MT Framework engine
MT Framework 2
Capcom's MT Framework V2
MT Framework 2
Capcom's MT Framework V2 (Materials Editor)