You made me curious, so I went exploring. In Google Images there is a search function to weed out licensable images. If you search on a word, then click on 'tools', then select 'usage rights', then select 'creative commons', it does bring up creative commons images, but you need to be sure you identify the terms of the licence in each case, and they're not at all clear in some cases. Upshot might be better. I've not used that one.