The last home I rented before I bought my first home had 2 big diamonds of red mulch at the base of two huge tree surrounded by gravel as the entire front yard. I hated it. Essentially a no foot traffic zone because any disturbance left patches of exposed weed screen and caused an unintentional intermingling of the rocks and mulch. It was almost unmanageable in the fall and winter. The leaves from two 60 year old ash trees could not be raked very efficiently and a leaf blower would just take the mulch with it. The gravel was super slippery with any amount of snow. Just awful.
On the flip side. I am on the tail end of a backyard rehab at my home. I dropped a large garage on about a 1/3 of the yard. Then created a fenced-in garden area right next to it and finished off with a small patch of Colorado bluegrass about 400 ft^2 with a xeroscape buffer between the grass and the neighbors fences.
I think a great value add would be a garden. Every house I've ever lived in (all rentals until 2017) the first thing I do is clear a spot in the backyard for a garden. I would have loved to rent a home with a fenced off area ready to plant. I imagine if a tenant didn't use the garden as intended they could put some lawn furniture or something in the space and make designated hangout spot or maybe a dog run. Also, folks who tend to a garden may tend to the property with the same care. Just a thought. Best of luck! much love BP.