Yes, some things definitely work better than others... Much as I love black and white, it's a lot more difficult to make an attractive b/w icon than to make a coloured one. Then, also, pictures that allow you to zoom in to a detail yield better results than others. If you try (or have to) show too much, it just doesn't look good. You have to 'say' a lot in a small space. Sometimes it doesn't matter that the image isn't recognisable, but at other times it does.

But it's certainly fun to experiment :). The red horse certainly looks good! (Is that Die Brücke? I'm an ignoramus when it comes to Expressionism, though I do like it.)