I find the tiles in my bathroom absolutely awful awful but I do not know what solution to choose to make it disappear. Is it better to paint it, tile it over or apply a waxed concrete coating?
The simplest and most economical solution would be to paint your tile (or apply a resin). Start by grinding your tiles by sanding lightly, degrease them with detergent, rinse and let dry. Then all you have to do is apply a special tile underlay and finally your paint.
You can of course stick tiled on the old, if it adheres perfectly.
Finally there are today false tiles (Smart Tiles) easy to install on the old.
This may interest you