Anyone running Photoshop CS4 or above can download a free addon called pixel bender. Got some nice filters to use. The Oil Painting Filter is especially good. It can be downloaded for free at the link below.
Yes, the Droste effect is excellent. I used it recently ( http://365project.org/sturnus/365/2013-01-28) - sorry to advertise my work but it does give you an idea of what you can do using it..
http://www.adobe.com/devnet/pixelbender.html