its randomization, not animation.
tcoords left top right bottom texsize numimages sinc
texsize is pixels. use 1 if you want your texture coords to be specified as normalized (ie: 0-1) texture coords, otherwise make sure your image is square.
typically you'll want to pinch the texture coords in by a pixel, so they don't conflict with the atlased image stored in the neighbouring cells.
numimages must be >= 1 (or omitted). really if sinc is 0 then numimages could just as well be any positive integer you want...
if you want actual animations, you can embed shaders into your particle script (you can embed glsl into those shaders and adjust the texture coords based upon the vertex alpha), but this requires glsl-capable drivers.
(you can also use animmap, but you won't have any control over the starting frame that way).