depends on the quilt pattern. on some you can add more blocks. on some enlarge the blocks. (i do that a lot). some add a border or enlarge one. some eliminate the border and replace it with another block.
i like to bump up blocks to a larger size because i don't like to work with 2.5 inches. they make my eyes hurt. i just redraw the patterns on graph paper to the size i like, usually 3 inch increments instead of 2.5. then i follow the instructions. that little extra goes a long way.
i agree about the queen size thing. they're hard to find. with a little 'managing' you can get it to the size you like. i can get it to between 94 x 94 and 98 x 98, just to where it covers that stupid extra high box spring and mattress (i won't be doing that again real soon), and hits the top edge of the side rail.
the easiest is to paper piece an just enlarge the pattern.