Hello, can anyone please suggest some thing I can do with the free version to get better graphics? I would really like to know some suggestions. 
Have good art. Unity Pro won’t magically make your graphics any better.
–Eric
I’ll go for the obvious : hire a better artist 
It’s meant as a joke and yet not completely because the following is pretty much always true :
great engine + poor graphical assets = ugly game
poor engine + great graphical assets = beautiful game