Quote: ", the map didn't really have ANYTHING. Just walls, guns, and some crates. I don't know why people can't understand that,"
I think the fact that you keep stating this is one of the problems - it's not that people don't understand, it's that YOU don't understand what they mean. The screen you posted from UT is the perfect example:
From what I gather, you see the screen as lots of walls and 2 boxes.
You know what I see? I see the trapezoid (Yes, I had to look that up) opening in the wall, the slanting archetecture, the shafts of white light, the ambience, the colour of the walls, the light sources, the size of the boxes. Make the map your own, but at the same time, these are all factors that make that a great looking map. There isn't much in it, but it certainly isn't bland.
There are so many things on the forum that could help you recreate some of this and ultimately make this into an excellent learning experience - sadly, I'm out of touch with the goings on on the media forum, so I can't really point you in a specific direction, however:
Look up Cosmic Prophets free scifi packs - they are incredible.
If another member can confirm this, I think Butter Cutter is free now? You might want to look that up to create shaped doorways and such.
Another confirmation needed - Wizard of Id had some excellent segment packs, but I'm unsure if any can still be downloaded.