A variation to the very neutral, tan coloured wiggle dubbing, here is an olive version:
A 'gaggle' of peeping caddis:
It is also worth a try mixing the dubbing. Also, leaving sections of patchy colour also help suggest alternative cases. It's interesting to see how the cases can vary from river to river. This weekend, whilst down in Devon I found a few caddis with very scruffy cases made from sticks and other detritis, whilst in other streams they tended to be more stone-based.