Looks like the ground cover in the centre is HC - Hemianthus callitrichoides (or dwarf baby tears) - which requires high light to grow densely and preferably CO2. The other cover looks like lilaeopsis, needs moderate light to grow densely as well I believe, and CO2 would be helping that along a lot also. Sides of the tank look like dwarf hairgrass, which probably needs moderate lighting.
The problem with axie tanks is that they don't like light, so you're fairly limited in your plant decisions and you must remember that this is their home and should suit their needs. It would be really nice to have a beautifully planted tank but it is not always as easy as we would like in an axie tank as additions like plant ferts and CO2 can possibly be detrimental to axie health.
There are plenty of low-light plants that people have grown successfully in their axie tanks. I have water wisteria, bacopa, vallisneria, java fern, java moss and anubias growing fine in my tanks.
The best thing for creating interesting scapes would probably be to use mosses, which don't need a lot of light, can root to things and can grow really nicely - as they have done on the trees here. There are lots of uses for mosses, I've seen some
good articles about moss ropes which can create a unique effect in your tank.
This is probably a good option to create new dimensions in an axie tank, and I'm sure axies who light to float would probably enjoy hanging off of it.
As for ground cover... that is a little bit harder in an axie tank, especially because they spend so much time on the bottom and tend to rip up anything and everything. I had lilaeopsis in my tank at one point, I had a crappy light though and it never really seemed to grow, plus it got ripped up occasionally. Though maybe others may have had success... might have to wait for someone elses input as I haven't had any success growing ground cover plants in my axie tank
And for reference, I believe this thread was incorporated into this article:
Axolotl Sanctuary