I've been experimenting with creating animated svg's to reveal an underlaying image. Here is my progress at present.

The svg's about 30Kb in size and overlays any image to reveal it. It's just a mater of placing an image on your page and overlaying it with a reveal svg (both need to be adjusted to the same size).

The svg's must match the page background colour (flat of course) and whilst the svg's are currently set to a white background it is very simple to edit the svg in notepad or notepad++ to change this value.

If anyone is interested in using this idea please let me know and I'll explain further.