Need thumbnail grid for wp site

New to wp. I am building a site for an visual arts organization and have used 1 step install for wp. I need to incorporate a grid on the home page where I can put up thumbnails that link to our 20+ member sites. What’s the easiest way to do this? Do I need to find a theme that incorporates a thumbnail grid or can I create an image with links in photoshop and upload? (seems there must be an easier way?) Is there a widget that I look for in a theme? or anyone have a search term i can use when searching thru themes to find an appropriate one? Thanks!

Try looking for a gallery widget (not sure there is one but worth a search) or look for a theme that has a gallery option.