Eclipse TFS Plugin says that a lot of files includes images (.png, vs..) have been edited although I have made no change to them when I open the "detect local changes" tab.
I understand the files in bin/ folder are supposed to have been edited but I don't understand the other files as I mentioned above to be seen as edited by TFS Eclipse Plugin. Is there any idea of its reason or a solution for it?
When you're using a Server workspace, TFS treats any file that does not have the Readonly bit set as changed. That's how Server workspaces work.
If you want TFS to reflect the contents of the file you will need to "Undo unchanged", which TFS will automatically do when you check in (TFS never creates two revisions when both have the exact same contents).
Or switch to a Local workspace, in which case TFS will store a copy of your file in a hidden folder, so that it always knows what your workspace version looked like when TFS served it to you.
TFS 2010 does not support local workspaces. Also note that TFS 2010 general support ends July 2015, it's really recommended you upgrade to TFS 2013u4 now or TFS 2015 as soon as it releases.