I want to change my current theme so that on the home/archive pages the featured image thumbnails (from the excerpts) have an image overlay that represents the category the post is in.
I found a tutorial that tells how to get the category name overlayed on the featured image, but I want an icon to represent each category: http://wplift.com/how-add-text-featured-images-different-scenarios
Here are 2 examples of what I want to achieve:
1) http://thepioneerwoman.com/?s=something&submit= -You'll notice that each category has an icon that is displayed just before the post title. (Butterfly, camera, house...each one of these represents the category that the post is in.)
2) http://www.torispelling.com/ -Here there is a circular icon with the category name, and it links to the category page.
If there has to be changes made to the actual image to get the overlay, is there a way to only make the thumbnail affected so that the other featured image sizes don't have the overlay (so they can be used in a slider for example).
Any help is appreciated!