I've volunteered at a cat shelter. Knitted blankets are not a good idea, because cats' claws will get caught and/or the blankets will get ripped up. I've had cats for 40 years and know them pretty well. The shelters around here always ask for old towels, and when they get ripped up, the shelters throw them out. Felted items still have the underlying stitches, but I have no experience with them, and my own cats gets their claws clipped every few weeks.
Did you ask the shelter what they need?