DermIS -- Dermatology Information SystemDermIS.net is a collaborative effort of the Department of Clinical Social Medicine (University of Heidelberg) and the Department of Dermatology (University of Erlangen).
According to DermIS, the site contains "the largest dermatology information service available on the internet." This very comprehensive database of images is searchable by text string or alphabetically and often has a number of images for a disease. You may find some disease names which do not yet include images.
Fitzpatrick's Color Atlas and Synopsis of Clinical Dermatology by 
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