... but you are restricted to make a difference between the file extensions only, aren't you?
Probably. Haven't tried anything else and never needed something else.
If I don't need certain files (let's stay at e.g. .bmp), I move them to a dev/temp folder which is not referenced at all in the project.
This way I keep my project as clean as possible.
Now I only need to find a way to dump all those temp files generated by WED into some sub folder. I thought this was possible, but can't remember how to change this...
I'm getting offtopic...