What are some good flowers to plant for my dog who passed away?

My dog had to be put down today. We have no idea what was wrong with him, but the vet said he was going to cost too much to be helped…and that it was a “lost cause.” Anyway, we found him in my moms garden and now my mom wants to plant flowers there for him. What are some kinds of flowers to plant for his passing? My mom is thinking a rose bush, but roses are too cliched in my book. Do you know any good sites that tell the meanings of flowers? :( He was our dog for ten years!