There’s something about lost items that I find interesting to photograph. I’ve got a photo somewhere of a pair of dress shoes sitting on a park bench–with no feet in sight. If I find it, I’ll have to post it here.
In the meantime, while the subject matter isn’t experimental, the processing technique is. I’ve used GIMP to touch up photos and, occasionally, to selectively color black and white photos. But every time I’ve done the latter, I’ve just let the original color shine through the black and white filter.