I am wondering if anyone has plumbed their supply and drain lines through a wall rather than the countertop? If so, did you do anything to "dress up" where the drain and supply lines enter the wall? In my case, it would be going into regular drywall. I thought about something similar to an icemaker supply box or a washing machine supply box, but those are both awfully big. The amount of wall I have access to is pretty short.
If you are interested in photos of the setup, they can be found here: https://goo.gl/photos/QH4CY8qJHuR2YDm7A

Creative ideas welcome!!

If it were me, I would just put the hole behind the espresso machine or grinder so no one can see it. If that wasn't an option, I would make it look like an outlet. I would get a blank plate, drill the proper sized hole through that and attach that to the wall.

You probably already know this, but make sure to not use flexible tubing in the wall for the drain. It will start sagging and cause backups. Use PVC pipe once inside the wall for draining.

I did near exactly what justneel described. If I ever change things I'll just get a blank cover plate and cover it.

Bob_M did you use an electrical box, too or just a blank plate. I kind of like the idea of an electrical box and a blank plate. I could use some rubber grommets, too, to ensure that the lines don't get abraided.

I used an electrical box.I filled it with a jb weld like slow epoxy and ran a 3/8 copper tube thru it...with appropriate threads on both ends..I forgot what the more distant thread was called but it is the yankee equivalent of that bastardly and ubiquitous thread known as british pipe thread...we mounted it with nails to a stud..It has worked flawlessly through 8 years of espresso bliss..

Feed it through a cable faceplate.

My setup is plumbed through the wall. I drilled a 2" hole with the bottom of the hole flush with the counter. I routed the water, drain and power through the wall and into the cabinet below. Inside the cabinet is also a 2" hole, just as behind the espresso machine. In the wall, on the drain line is a brass 90 degree elbow, allowing the drain to function properly. The installation is simple and the fact the machine covers the top hole and the bottom hole is in the cabinet, all is well.

We just had the back splash tiles drilled instead of the counter. I would also suggest easy access with view to a quarter turn ball valve cut-off for servicing and vacations.

We also got a reduction in own home insurance policy when they saw that the direct plumb and drain installation were properly done by a licensed plumber, as was the 20amp dedicated line with a GFCI receptacle for the grinder and espresso machine, done by a licensed master electrician.

Mount a cherub statue on the wall, run the line through its mouth.

Works great running through the wall and completely reversible unlike drilling a counter top would be. I needed to get through the backsplash so i cut out one tile (roughly 3in tile) and ran my lines down and back in through the lower cabinets. I'm currently running off a 5gal water jug which I switch out once a month when it runs low. I'd highly recommend using the wall, with my machine in place it is not possible to see the opening behind my machine.