When using Mod Podge to seal your photo tiles and you want to avoid brushstrokes, take a piece of sponge and stipple it on top. You could also use a clear spray lacquer instead.
You won't be able to tell there is any finish on the items in the photos. The smaller 2x2 tiles have a magnet adhered on the back. The first small tile was used as a party favor for a 100th birthday, and everyone loved them! One of the tiles is a photo taken in the rain, that is not Mod Podge brush strokes. The larger is 5 x 7 photo that I mod podged to canvas and then stippled Mod Podge over the photo.
There are many ways to ways to use and repurpose ceramic and glass tiles to create something unique. This page contains crafts using tiles.