Dress the part
If you’re getting married in IMVU and it’s important to you dress up. You don’t have to rent a tux and nobody may see you, but dress up. It’s hard to explain but it gets your head into it and you will enjoy it more.
Why not take it a step further and try to make at least one outfit in IMVU that matches clothes that you have in real life. Don’t go crazy and do this all the time or you will be really really crazy. But a little bit crazy is fun, and worth the effort.