The HiRise imager in orbit around Mars shoots a continuous stream of data about its surface our way. Nasa’s posted 44,000 images so far, each available in all sorts of formats and projections. You could have one a day as your desktop background and never run out.
Gullies in Dunes Dubbed Kolhar.
Yardangs South of Olympus Mons 
Crater-Exposed Rocks of Yalgoo Crater in Isidis Basin