Tips for spicing things up in the bedroom?

My husband is super vanilla and oh so sweet. I mean, he is just the sweetest, most gentle person. Well, after 7 years of marriage...I’m starting to get a little bored in the bedroom. He literally just wants me on top all of the time. In our bed. Nothing adventurous. I told told him that I wanted to start trying some new stuff and spicing things up and he’s willing to try. I just don’t even know where to begin because we’ve been doing the same old thing for so long. So, give me some advice, ladies! What are some things we should try?? (Keep in mind that he has really bad knees and nerve damage in his legs)