I see the point of choosing colors that matches the image, but a frame would help to smoothen out if we chose other colors, for instance, a narrow line at the top and bottom of the image. The CCG Magic:the gathering seems to solve this by having the artists stick to colors that matches the color of the card he is going to design.
An example of how colors distorts perception - the white tiger card (from "cards") is so blue that at first I thought it was a water animal.
My suggestion is that background color is fixed to terrains, for exampledesert - sandforest - forest greenfreshwater - bluegrassland - green or yellowocean - navytundra - violet or grayand at last, maybe
event cards should have their own color, too?
These colors should be pale, as said previously, to save ink. This would allow cards to be quickly identificated, simply by color. In black and white print, we would still have the symbols at the bottom of the cards for that.
When a species belong to several terrains, colors could blend in from different corners.
I really like the new card design used in the coral reef deck, where the image fills up all of the card, and background colors are transparent.
Example: this is a special lion living in both deserts and grasslands. The terrain symbols would be there somewhere in the bottom, too.