It says: Failed to load image
Please make sure that this file is in place (relative to the executable).
Re-install CS2D if you are unable to fix this problem manually.
And I'm using a mac
That's weird. I already got a report from someone else with the same problem but I don't understand it because the file is in the archive for the mac download. To fix it you can try to download the windows zip archive and extract it into your CS2D folder on your mac. This should add all required files.