I don't mean to burst any bubbles but even if you allowed some sort of grid-snapped-repeating-texture thing to the panel object to allow this, then you would pretty much be stuck building your level with rectangular shapes anyway:
<img src="http://i25.tinypic.com/inbyiv.png">
That's rather limited. You wouldn't be able to make any complex, seamless shapes, and you'd have to be placing all sorts of other single tiles anyway. More trouble than it's worth, imo.