We got a Frehiten sectional sofabed from Ikea for our family room. I can't decide what kind/size rug to put under it. Please help!

The Frehiten converts to a sofa by pulling out a sleeping surface that's on wheels. It's almost like a drawer that you pull out from beneath the long part of the sofa. Because it's on wheels, the rug would have to go all the way back to the wall so the bed part can be pulled out easily. (I tried using an old rug, but it wasn't the right size and the wheels got stuck when I tried to pull it out.)

Can you give me ideas for a rug to put under the sofa? I'd prefer something bright/modern. And kid-friendly. :)

Here are the dimensions:

Length: 90 1/2 "
Depth: 59 1/2 "
Height: 26 "
Bed width: 55 1/8 "
Bed length: 80 3/8 "

Thanks!!!