Amazon has those "Text and Image" Links. They have a small size and a large size, but both seem too small for me. Is it allowed for me to switch Amazon's image with my own?
of course its allowed, write any text, use any image but it should relate to same product and model which you are linking
use a larger image and link it with the affiliate link, some basic html knowledge will do should be smth like <a href=""><img src=""></a>