You have my sympathy OP, when my late father in law died, my husband and his family ended up filling several skips worth of what were essentially bits and bobs, things accrued over the years with "I'll hang on to that in case I need it later mentality" which I think was a mindset prevalent amongst previous generations. Husband and siblings were quite ruthless in getting rid of most of it and keeping some choice items and really as long as there remains a few things to remember your MIL by, maybe they could be incorporated into your home without changing the character too much. We did get some of my late mother's bone china, a couple of lovely, fairly old fashioned tea sets, often the sort of china used in really nice oldy worldy tea shops. I love them probably more than my husband does, somehow I don't think my boys will be interested in acquiring them one day
I don't think any of us took their ornaments, Lladro sort of stuff, I'm definitely not keen on that type of thing personally, previous generations seemed to like ornaments around, I guess we are all of our time, the only clutter I really like are books.