does the wall plate come in only one design?

Yes

Wallplate shown is the only design Lowes has. The company that makes this unit also has one with a toggle (up/down, not Decora) style switch, but Lowes doesn't carry it.

The cover appears to be integral to the switch box, and the faux screws are a design detail, not functional. You could probably cover it with a vinyl decal, but I don't know if you could attach a different cover, that better suits your decor, over it, as it might interfere with the signal.

Yes, just one design. Looks like a standard switch plate but is slightly thicker. I thought I could use a dual cover since I placed it next to an existing switch, but you can't. The switch is part of the cover and can't be separated, so you can't substitute a different cover