It looks like it can be higher quality (idk how to get really high quality sfm stuff, never got it to work. Also try messing around with lights and darkness (you can make it look a lot better with good lighting). Looks like you have only used normal presets for the character, try to move the arms and stuff, and try some close ups :)

Lighting is everything. Try avoiding dark characters/players.
Rule of Thirds can make for some really cool looking posters.

Also what's with the lighter, borderlike edges on the right and bottom? Are those intentional or what?

no they just appeared there and i dont know how to remove it, looks nice with some posters but not all

imo the lighting could be a little better? maybe different is what i'm looking for. maybe both. something outside of the tf2's vanilla lighting. take your loose cannon demo screenshot for example. that's good lighting. the only problem with it, i feel, is that the lighting is coming from a source off screen where a light doesn't exist. if i remember correctly, there are lights directly above there, so duplicating what you have going on but from above would look neat.

all in all, i like what you've done. just work on the lighting and you'll be good to go.

Possibly blurr out the background so the main focus is on the character.

1. Use a lower FOV for the cameras. Try using the lens presets built in SFM, the 50mm preset can give you a nice general look. With this high FOV you get a lot of distortion and it doesnt look very good.

2. Try better composition. Use the rule of thirds. Pay attention to how high the camera is positioned. If its looking at the character from above, he seems smaller, less dominant. If the camera is looking at the character from below, he is dominant. Use this to communicate what you want from the poster.

3. Use depth of field, maybe tweak the SSAO to get a better look. Even if you dont want the background blurred you should still use depth of field with no aperture, because it eliminates the black noise.

4. Lighting - google 3-point lighting setup. Dont use just white lights, use some colored ones too. If youre outdoors, the sun is generally a orange/yellowish color. You can use a blue fill light for contrast.

There is much more that could be said, but have this for now. Good luck with future posters!

Yeah, like other have said, lower fov and better lighting.

Here is one i have made, the low fov and the lights behind it make the picture halfway decent.

http://i.imgur.com/I6SgfRM.png

Its odd how my soldier's hats aren't actually pink in the sfm. I guess its a lighting thing?