Swifts are primarily insectivores, so they wont be nibbling on your plants. But as a practical consideration, swifts are both avid climbers and burrowers, so it would be quite challenging to find a live plant (and a substrate to contain it) that will hold up to the constant climbing and uprooting that the plant will experience in that smaller space.
For climbing, I would provide some upturned slabs of rocks or bark, or pieces of driftwood or other branches that are wide enough to allow him to perch comfortably near the top.
For a substrate, I would stick to things like sterilized soil and fine grain sand or something like coconut fiber or reptile bark (what you have looks fine).
Consider also that, for an enclosed space like that, plants need soil that will need to be watered regularly. That will attract and harbor insects as well as mold and fungus which can thrive in that enclosed environment.