A few variations - doesn't include a mascot but is very brandable.
Sleep Republic
Sleep Revolution
Rest Republic
Rest Revolution
Head across to Graphic River and stick either Republic or Revolution into search and you will get some very strong graphics.
Guests are no longer guests they are citizens of Sleep Republic for the night.
Graphics wise you can go a couple of strong directions just depending on your marketplace.
You could go for a bit of a hippy look with a hand up in a peace sign.
I'm a massive fan of Russian and Vietnamese revolutionary artwork. It's very bold and I can see walls of a hostel having murals of that type being used (with a modern twist of course).
It may not work in mid-west USA, but for many places around the world it would work well. With guests of hostels typically being young you could use such imagery to be seen as a little bit 'on the edge'.
Hope this is a little bit of food for thought.
Cheers,
Phil