Non-traditional I know..for my dearly departed husband.. he is getting a .hand painted stepping stone instead of the traditional stone/granite..bought a 12x12 stepping stone at Home Depot. I painted it a light blue colour (outdoor paint).
I've got some black sign paint , used the computer to generate the words and dates so all evenly spaced...
Mod podge some pictures on there , seal ...
I painted some poppies on my dads,, he was a veteran
Actually it looks pretty good..
So I have to maybe explain to certain family members as to why I ain't getting him a traditional headstone..
I can do it..I've got the answers

The cemetery accepted this?...or is he buried in the backyard?

The cemetery? What do they care? They don't want fences or problems for the grass cutter.. this cemetery is in bumfuk nowhere, rural,
I'm going to place the stone on top of the urn once it's buried..so I and family will know he's directly under the stone..

Now that's a very good question
I sealed the cement first.. used outdoor paint. And sealed it with many coats of varathane..
I hope it lasts a couple years ..and I will work on ordering a traditional one for long term ..but I would still want something less traditional in style.. so much ideas on the internet..
A childhood friend of his has a rock quarry, so using a stone from him would be appropriate .

I see nothing wrong with it... But as some has asked how long will the paint last?.. But you can always get a stone of your choice from his friend and get it engraved then add your touches to it too...

I think it is awesome it is the unique ones that most in the future will remember..

Myself I have told my kids I want to be cremated and my ashes spread... Take a cruise and pour me over board~~