Color splash photos are those that have been converted to black and white, but one object has been left colored. Sometimes, it's easy to just isolate your colored object and you're done. Other times, more editing is required, such as adjusting color levels/light/shadow/etc.
Any photo is fine, as long it has selective color and you haven't posted it before. You can read more about CSS guidelines by clicking here.
CSS has been temporarily relocated for today. You can link up over at Mars Pics and More!