Also make sure to type jpeg_quality 100
So its as best a quality as it can be.
Also this is a very handy resource:
http://developer.valvesoftware.com/wiki/How_To_Take_Screenshots
So I ran through the level, a few things:
Never use hl2 textures, half lifes art style is distinctly different and doesn't fit at all. Same with the hl2 sky (to change, go to: Map<MapProperites<Sky Name [heres the list with all the skys:
http://developer.valvesoftware.com/wiki/Sky_List])
Second, the map feels like a great big box with buildings, props, and other obstructions thrown in. Rather than one 4048x1024 wall use several, smaller, varied buildings/cliffs to make it more interesting. As it is boring and uninteresting to fight in.
You also have alot of corridors in your map which dont work at all in tf2. Theres alot of close, tight, prop-spammed places especially near the final points.
Lose some of the death pits, it was cool in lumberyard as well as nucleus but its getting played out. I could understand the gorge's but the spikes by the final point is about as unnecessary as it is annoying.
Never copy things from Valve maps, I know its tempting but you don't learn anything that way. Use them as they are provided for, reference. Look at them and see how they made this look interesting or how they attracted your attention towards something.
Finally try lowering the color value/brightness on your lights. The yellowish is very distracting and overwhelming. Also your displacements need alot of work. If your going to set your map in canyon, you'll need to smooth out those displacements, the spikes coming out of them look very unnatural.
Don't stop working at it and youll eventually get it, just takes time.