These are not paint by numbers, or fuzzy posters, simply high-quality line art posters by assorted artists. Each print is on paper that is intended for use with Copic markers.
Here is a close-up of an undersea poster that I am in the middle of coloring. It takes a long time to color each poster, but in the end it is really worth it!
I wanted to add lots of blue to her skin, as this mermaid is underwater, so I colored the skin with E000, YR01, E13, and E15, then added additional shadows to the skin with Boo, to give the hint of blue water. I colored the eyes and lips with BG13, E04, R14 and C3. Her hair is colored with a base of Y11, then I added E42 and E13/E15 for the deepest shadow areas, with a few dots of E04. Her tail is colored with E000 for highlights, then B00, BG13, B12, for the blue areas, with B34 in the shadows. The fringe/fin is colored with E000, RV02, Boo, and BG13. I threw B12 in the deepest shadows on the fringes and fin.
I hope you get a chance to order a few of these posters, and have fun tackling them.