XF 1.5 Different user (banner) color based on posts / custom user image?


Currently in the finishing touches of my migration from vBulletin, have got two questions:

- In vB it was possible to assign different user banners to the same group, based on a user's group count.
Would like to have the same in xF as well, but can't find any option.

Relevant user group:


How it currently looks:

My target is to have a green "Member" banner + name once a registered user has reached at least 20 posts.
How would I go about doing that?

- Similar area as above. From time to time, we organize contests where participants can win forum reputation points and a custom image underneath their name (along with some other stuff).
This image would be shown right underneath the banners in each post for this user. In vB, I created seperate user groups for each winner and assigned the image to it through a rank.
Could do the same in xF, but I am looking for a more elegant solution for that, as I already have 6 extra user groups just for that (quite a pain to manage).