Where to start and end kitchen backsplash?
Not what you're asking about, but important:

If you regularly plug in more than 2 devices, as implied by the 6-1 gadget in the picture, then I highly recommend putting in another dual 15A receptacle a few inches away from the existing one. It can be on the same circuit and on the load side of the existing GFCI. I would put it a few inches away (either above the existing receptacles or to the left, below the light switches - presumably there is a stud between the switches and the receptacles) rather than putting in a 2-gang box because many devices need extra room (e.g., wall warts). It can share the same circuit so the cost is basically standard dual 15A receptacle + box + a little bit of cable and appropriate clamps, etc. This solves two problems:


For now and the future it eliminates the extra plug-in gadget to "expand" the receptacles. I use those, but I hate them. When there is a specific need - e.g., provide surge protection, then they make sense. But when they are just to add more receptacles they become another point of failure.
Doing this now, before you tile, means you don't have to do extra work patching. If you do a half-way decent job, any mess (extra holes, scratches, etc.) will be totally covered up by the tile! Very convenient.