My wife was making all these custom minis for her friends and wanted some kinda way to display them. Came up with this pretty basic stand. Has a raised platform in the center with a hole in the center if it to place a magnet inside. 
The platform is 32mm diameter and accepts a 12mm diameter magnet. The way wifey did it was using the same magnet on both the base and the mini, but you could also likely use a washer or maybe even soft magnet sheet.
Can be used as printed, but obviously if you are into painting minis you will want to decorate the stand. Maybe not to the degree that she did though. Lol