In my state AFAIK as long as the state name and registration sticker are visible frames are fine. Will say tinted plate covers should be illegal regardless as that tends to make them impossible to read even 20' away.
In Maryland if you don't return your tags you get nailed. .. a fine per day.
No insurance seems to require you to hit someone first before they take action
The wife’s ten year old license plate frame. According to the NC DMV, it’s illegal. She’s such a rabid Duke fan even though N.C. Is a one plate state, I’m not about to tell her we’re going to have to get rid of it.