If you're unable to visit the colorful ridges and hills of Landmannalaugar, Trölladyngja is your next best option. The area is colourful due to fluctuating intensely high temperatures, a few mud pools and solfataras. The road here is quite bumpy but in good conditions and careful driving, any vehicle can make it. Be sure you allow for extra driving time. I do not recommend coming here if roads are icy or snowy.
If you want to play it safe and be in a well-equipped, photogenic car, then you should rent an old-school Land Rover Defender from www.isak.is. Use the code "gunnar" for renting your Defender on a special price.