iconCompo

iconCompo can compose one icon out of two images mainly for making custom folder icons. Drag and drop one or two images onto the main window of the program and then adjust the images in various ways - position, size, directions, transparencies and colors, text.

Composite images can be attached to existing files/folders, used to create new folders, or saved in several image format such as icns, png and tiff.
With a Finder contextual menu item iCCMPlugin, you can attach custom icons with your saved settings or add thumbnails.