A challenge is that I hate fan noise, and this was going to be running all the time. The computer I bought was a Compute Stick from Intel, and I thought I was buying one with passive cooling, but when I plugged it in to my horror it had a small fan! I could return it. But instead I mounted it inside the wall, and set about writing a 4K 60fps dynamic slideshow that used so little CPU/GPU that the fan hardly ever kicks on. I am kinda proud of that.
I also got to add fun features, like showing album art for whatever was playing on Spotify, but the best one is the Faaland (Weasley) clock.
On every family member's phone I set up IFTTT with location tracking. When they enter or leave areas (eg home, school, work) it sends a message to a web service. The slideshow then monitors that service, and updates the hands of a clock with our faces on the hands. If someone has changed location, it chimes. The inspiration was that everyone could know when I left work (and so when to expect me home), but it's one of the family's favorite things I've done and (to my slight surprise) all of them wanted their location tracked on it.
Fun facts: the battle at the end of the Harry Potter series occurred in May 1998 -- shortly before the release of Windows 98 and the founding of Google -- and I am one year younger than Fred and George.