Originally Posted by
PaperPrincess
Most mattress tops are standard sizes, but it's your choice on the length of the fall. This can really effect the finished size. Also, there are different types of twin mattresses. You need to get the exact measurements of the mattress top, then decide how far down you want the quilt to hang.
Your general idea of alternating blocks is a good one.
I agree with PaperPrincess. Find out what your size should be and take it from there. If you want to keep it simple with a focus fabric of cats, you might want to look at the pattern Warm Wishes. It is a free pattern.