Bases for models

Hey all, im fairly new to warhammer in general ive painted quite a few models now but I havent done anything with the bases. Im very new and just looking for tips or ideas on how to make the bases look cool for my sylvaneth.

Should I have not attached the models to the bases and prepared them first ?

Appolgies if this is too broad an ask!

(Im painting the army in a winter/frost theme with lots of blue white silver if that helps)