Deepest visible light image of 10,000 galaxies - https://www.spacetelescope.org/images/heic0406a/zoomable/
NGC 1866 star cluster - https://www.spacetelescope.org/images/potw1847a/zoomable/
Runaway galaxy UGC 10214 with thousands of galaxies in backdrop - https://www.spacetelescope.org/images/heic0206a/zoomable/
Abell 2218, a rich glaxy cluster composed of thousands of galaxies - https://www.spacetelescope.org/images/heic0814a/zoomable/
Gordo ("The Fat One") - enormous galaxy cluster with mass of three million billion Suns - https://www.spacetelescope.org/images/potw1802a/zoomable/
Gallery of more of these at https://www.spacetelescope.org/images/archive/zoomable/ - follow a delightful thumbnail, then desperately seek the tiny buried zoomable links on subsequent pages.