Painting over engraved tiles

Hi, I would start by Cleaning the tiles to remove any dirt or mildew using an abrasive bathroom cleaner. After cleaning, wash the tiles with clean water and allow to dry thoroughly. There are products on the market to fill the engraved patterns and also the grout lines if you wanted them hidden also. You would have to fill and sand the tiles in stages to achieve a smooth finish. Building up the layers as you go. Filling Sanding - Filling Sanding until smooth. Finish by lightly sanding the the whole are including tiles with a fine grit sandpaper, such as silicon carbide or aluminum oxide with a grit of 220 to take the gloss finish off the tiles and smooth the whole area. An orbital sander will do a faster and better job than hand sanding. Wipe down the surface with a damp cloth to remove any dust, leaving it to dry fully. You are then ready to paint the tiles although colours are limited probably to about 15-20 colours. Use a good quality paint such as ronseal one coat tile paint from dulux. It's waterproof mound proof great for kitchens and bathrooms so it's hard wearing. Don't try to cover in one go take your time and give it two coats for a better finish. Avoiding over application of paint. Hope this helps.