I know back in the 90s we all wanted larger and larger sprites, but to be honest, I love low res games with small, well done sprites, they feel like they make better use of the screen. Look at Lazycow's Tigerclaw for an example!
My suggestion was in case you had not seen any of those. To be fair horizontal scrolling Danmaku-type shmups aren't my favorite, I usually think they don't work great (many times do suffer from sprite elephantiasis :P), but here's looking forward for you to change that view
My CD32 is waiting anxiously