Can I meet any legal issues if I put game wallpaper in my site as header? For example lets take this wallpaper link
Most gaming clans use screenshots as headers and there's thousands and thousands of these sites. So I'd say your 100% safe. Of course if you get extremely successful there's always the element that you might get hassled to remove it.
Wallpapers are made freely available for use. I don't see where there is a problem with using them for a header or anything else.
If wallpapers are made free to use does not mean free to use it commercially. Only free for personal use.
Sometimes there will be a disclaimer that images are not for commercial use, but I have never seen such a stipulation with wallpapers. As far as I'm concerned they are free to use photos. Does anyone know any different ?
Technically speaking, you need express permission to use anything you did not create yourself. I've seen wallpaper sites that allow only non-commercial use - and without a disclaimer/tos granting usage, legally you need to get permission.
Now that you mention it, I guess I have seen that 'Not for commercial use" tag on wallpapers. I guess the OP would just have to check the terms and conditions for use.