Can I leave painted stones on a headstone?

I’m sorry if this is a repetitive question but my grandpa recently died and he was Jewish. I didn’t grow up practicing judaism so I’m unaware of certain rules I guess. I recently found out about the visiting stone and I wanted to ask a few questions. If anyone is willing to answer them, it would be very much appreciated.

1. So I wanted to leave a painted stone but I wanted to make sure that it’s allowed. I was going to paint a stone that says “worlds best grandpa” because I made him a hat a few years back that he would wear everyday. Would that be okay?

2. My sister made him some roses out of ribbon and I was wondering if it would be okay if we placed them? Like if this would go against anything.

I’m sorry if these are dumb questions, this is my first time losing a loved one and I don’t want to do anything wrong. My aunt got upset at me for putting a flower in his grave during the funeral but I didn’t know we weren’t suppose to because no one told me that it wasn’t okay. I just don’t want to mess up again.