Images for older children may already contain small parts, complex narrative compositions with greater color palette. The outline is more subtle. These can be supplemented with coloring tasks. For example, to write the missing word, or paste a sticker, finish drawing, connect the dots.
Today there is a large set of coloring books. You can find coloring-cursive books, books outliners, for boys (all sorts of appliances, machines, robots, etc.), for girls (fairy-tale characters, dolls, funny funny little animals). There's even a wallpaper coloring books that opens a wide field to have enough space for young artist.