You're on Windows, aren't you? Maybe it doesn't understand the / in the path. If I remember correctly, you can use dots. Like this: "maingame.graphics.pic.png". Otherwise, you probably need backslashes (\)
I see a small arrow on the lower right of test.png's icon. Have you copied the real test.png there, or have you created a "direct access" (or whatever windows calls them now) instead? The image should work, the direct access should fail.
I think Windows added proper symlink support in Win7 (or was it Vista?), but I don't think it's used by default from the GUI. So that's probably a "link" (as in a .lnk file) and yeah, that doesn't work.