I wouldn’t mind to have a few island themes to choose between 
Volcanoes and fire
Electrified islands 
Maybe an urban area 
The ideas are limitless for those! 
P.s. I lost my first castle lv17 as my phone was stolen last month
Rebuilding on my new phone now at lv15 but maybe you can add in a way to save progress  to Google cloud or something like that so anyone else doesn’t have to go through the process like me