1: Make sure your screenshot is not in the .tga format. If it is, convert it to .jpg - there are tons of good freeware that can do the trick.
2: Upload the screenshot on http://www.imageshack.us/
3: Copy the "direct link" and paste it in your unban request
4: Encase the link in img tags, like this:
- Code:
-
[img]http://a.imageshack.us/img291/2847/radukumures.jpg[/img]
You should also find the banrequest on you and post the link to it in this unban request.