If you haven’t come across the Icon Finder site then it is well worth a look.
Icon Finder is a search engine for high quality icons. Although it is primarily aimed at professional web designers there is no reason why your students can’t make use of the resources for their website design projects or for when they need to create a banner or logo image.
The icons are mostly available under a GPL or Creative Commons license so it is a good opportunity to remind students about searching for images that are not bound by copyright restrictions.
There are a number of different ways that you can search the site with filters for license type and image sizes. If you can’t think of a search term to use then use the ‘Browse’ menu to have a look through all of the icon sets.
There are currently almost 150,000 icons available in 731 sets which should be more than enough for most students students. If they can’t find exactly what they are after then they could always create their own and contribute them to the site.