I need to post these here as they're way cool. It was posted on twitter by tigsource's own
@Skydsgaard_ on the subject of handling stairs. (and other things as well for that matter). It was really inspiring and made me feel rather special that Skydsgaard took the time to look at this conundrum.
If you built the circular base for the model to stand on into the normal stair art (instead of having it morph into shape), it would create an affordance to communicate to players that they can end a turn or move on the stairs, which doesn't exist in the "normal" stair art (the player will have to guess if that's a valid move or not since it doesn't look like it can hold a model normally).
Alternatively you could do the morphing on mouse over to communicate the same affordance but keep the immersion of "normal-looking" stair art when not in use.