You can take up a course in multimedia or interior designing. It isnt necessary that you need to do a multimedia for that. You can complete your graduation and take up interior designing as a PG and while you doing this you can consider taking up multimedia which will be an added advantage to your interior designing.
I understand when you say that you dont want it to be as a main career option but something that you are interested in. Certainly you can do it. But while you decide on that also keep in mind what do you want to take up as a main