Felt most likely won't hold up to regular cleaning and will probably also lose color and bleed all over the place. The repti-carpet or marine/outdoor carpet (green in color, looks like grass, very inexpensive) are both far better alternatives.
I could see once it gets wet from spilled water and the normal gecko activities (feces, urates, etc...) that it would bleed and the get on the geckos feet. I think there is ALOT better choices out there. Just my 2cts worth.
I am going to be trying shelf liner. The non-stick, rubbery mat like stuff that comes in a roll at Walmart. It comes in brown & black. Just a suggestion, haven't tried it yet but heard it was okay to use and easy to clean. I have been using repticarpet (in my 20L tank) but notice their nails stick at times & their teeth too, if they are over zealous in eating food!