How about using one with a Remote Control,
Like this click here
Manual click here
The Remote could be encased (Slide-in/Out with locking device)in front of the Perspex case, with Holes in it to give access to the Prev/Next Buttons (11 on page 4 of the Manual).
To turn it on Press Power on Remote, Then Photo to automatically play slideshow.
How to watch Wimbledon 2015 live online: follow the tennis from your laptop or PC