In reply to Otto.

@Ryan Hellyer: Really, it's a problem with the default settings in various SVN clients. The SVN client sets the mime type, and a lot of them don't come preconfigured to set the mime type correctly for images. We're looking into other solutions in the long run, but if you want to not have to worry about it anymore, look at your SVN client's config settings for enable-auto-props.

If you use Windows and TortoiseSVN, look in your C:\Users\yourname\.subversion\config file. Uncomment out the line enable-auto-props=yes and the lines for *.png and *.jpg in the [auto-props] section.