They may not have the biggest names but they've had some hugely influential bands...Cocteau Twins for instance. It's not stadium rock but there's nothing minnow about them.
There's been loads of great Scottish bands over the years. They haven't exactly been slacking, in fact I reckon every part of the British Isles can boast great bands.
Off the top of my head: Alex Harvey,John Martyn (mainly), Aztec Camera , Belle and Sebastian, Orange Juice ,The Associates...