Oh, yeah if the cage is wood that could definitely be a problem, it's one of many reasons I don't recommend wood cages. Metal cages you can actually clean them if they get pee on them.
I would be careful with using a humidifier in the room especially if you have a wood cage. Make sure it's as far away from the cage as possible and it doesn't raise the humidity up too high. One big issue with wood cages is if the chin gets a fungal infection, like from the room getting humid, all wood in the cage needs to be thrown away since it's nearly impossible to get the spores out of wood. If the cage is made of wood that means the cage needs to be thrown away.
The second two pics both look like anti pill fleece, but I would go with the middle one since the grey ones look like the paw is embroidered on. A lot of people also get fleece throws from Walmart or bargain stores for cheap if you want different designs. I got mine from a local bargain store as well as higher quality fleece with specific designs from a fabric store.
Honestly the fleece might be more comfy then the towel anyway. When I first switched to fleece liners from just using shavings, my boys actually stretched out sleeping in the middle of the cage floor. It was cute once I realized they weren't dead.
(minor freak out moment) Just make sure you wick the fleece when you get it so it absorbs the liquid. If you don't know what that means, you wash it a couple times to remove the fabric softener they put on most fleece when it's made, it makes it looks and feel nice but also makes it less absorbent so the pee puddles instead of absorbs into the fleece. You will know it's good when it actually absorbs the water instead of coming out of the washer feeling dry. Also if you use throw blankets make sure you remove the string along the edges.