How about adding some generic body part TF graphics, to show hands to paws, feet to digitigrade, face to muzzle, etc? Don't have to be in color or too species specific, so they could be used for multiple TFs.
Of course, you'd have to have some way of either tagging the TFs, or a table referencing the TF to an appropriate graphic for the change.
The table would probably be the best way to go, since you could have TF specific change graphics that way, one for each shift....