I put this here just for fun. Between 2000-2007 I was very active in the modding scene, these are screenshots from TrueCombat:Elite on the Wolfenstein: Enemy Territory engine, which was the first free FPS game released that was moddable, and it ran on id Software's Quake 3 Engine. These screenshots are of 5 different maps I created around 2004 mostly before Half Life 2 came out. It would take me about 4-8 months to complete a level in my spare time. "Photo realism" was the big thing back then and it's what we strived for.
The times then were very different, BSP geometry was the standard, also mainly for architectural detail. It took half an hour to compile lighting and there were no real time previews of the rendering. There weren't any useful game texture resource sites and most of the textures I made myself using consumer grade digital cameras, which were a novelty back then. Shaders were text files specific to a texture which we wrote without any debugging tools. I created all the 3D props myself using MilkShape 3D, which was barely a 3D editor with an exporter incapable of exporting smoothing groups.
Skyboxes were these horrible computer generated things which even back then looked dated, I had found a hobbyist who created 360 wide angle photos of clouds and asked permission for us to use those. Our main programmer then converted these to cube maps in mathlab. It's just one example how to make a big impact with a small idea and some ambition.
TrueCombat:Elite was very succesul and with the major release I remember we had 800-1200 players online on All Seeing Eye (a piece of software to find servers) 24/7 for an extended period of time. We had players in every continent with many localised fan sites.
Skills used and developed: Level design, enivronment art, architecture, construction, texturing, texture blending, colour composition, lighting, shaders, 3D modelling.