A few we've been on:
Costa Rica - rainforest, wildlife including sloth, toucan, monkeys, raccoons, gecko, coati etc in wild, active volcanoes, hot springs, very high ziplines.
Finland - seeing brown bears in wild and summer toboggan, reindeer.
Norway - Fjords, polar bears (not done), moose safari
Australia - Scuba and snorkelling in Great Barrier Reef, stayed with lady/former vet that looked after injured tree kangaroos, possums, pademelon, bettong etc - had one of tree kangaroos jump on me and daughter bottlefed the bettong, we could feed pademelon and possum, seeing koalas, whale and dolphin watching from Port Stephens - saw hundreds, Sydney Harbour Bridge, Blue Mountains - wild kangaroos. Rainforest and crocodiles in rivers.
Cape Town - nearby penguins on beach, big 5 safari (not as good as others but no anti-malarials needed), Table Mountain, vineyards
Brazil - Rio - famous beaches, Sugar Loaf Mountain, monkeys, Paraty - old cobbled town with fishermen boats and horse and carriage rides / rainforest
Cuba - different but didn't like that much.
Hintertux - Snow all year round, cable car, ice palace under mountain
This year Borneo - orangutans, sun bear, rainforest, Perhentians, snorkelling, scuba, sharks, turtles, River Kwai - WW2 sites, bamboo rafting and zipline / hot springs etc.
Glad you had a nice time in Iceland, never been but did Lapland in winter and that had husky/reindeer safaris, snowmobiles etc and quite magical.