Anything that works in a savoury pancake, a toasted sandwich or a pie will probably work a treat!
I’d be tempted to try:
spinach and ricotta
Boursin , chicken and mushroom
pesto and chicken
pesto and roasted vegetables
chopped bacon, chopped sausage, scrambled eggs and baked beans
hummus and grated carrot or roasted vegetables
keema (spicy Indian mince with peas) - I would serve that with some raita
aloo gobi or aloo saag or any leftover curry (a bit like a filled dosa)
roasted baby tomatoes and cream cheese
what about a Hawaiian pizza style - cheese, tomato, ham, pineapple (I realise some people may think I’m a troll/should be shot for this!)
banh mi style (a Vietnamese sandwich that uses pate, spicy meat, mint, coriander)