Heh, I found it myself. Anyone who's interested:
Once you've got your texture animated, below the "Use Image Sequence" box that you've got checked, Maya has created an expression. You can see it in the "Image Number" box below, which has turned violet. (refer to attached image)
Right Click over "Image Number" and select "Edit Expression."
The expression will read something like this:
After "frame" simply add %x (where "x" = total number of frames to loop).
In my case, with five frames to loop, I edited the expression: