I designed a frame for a Alcatel Idol 3 Smartphone. The smartphone is not so expensive and has a good performance. I printed the frame with a Inkjet 3D Printer and prepared the surface with sandpaper. After this I have laquered it in white. In the last step I have mounted the smartphone in the frame. You dont need to open the smartphone cover. In the picture you see it without backcover because I testet something.
You can glue 2 or 4 Magnets in the frame to mount it on a wall.
I use a micro usb plug for soldering. The frame is mounted with magnets on the wall. I soldered the + and - for charging direct on two magnets. One the wall side the same. So you can put the smartphone easy with magnets on the wall and it will be charge. On the wall side i use cooper tape under the wallpaper. One tipp: make a bridge between data - and data + on the micro usb plug. So it will be charge with a higher current (ac).
But this only one option how you power it.