What can I put in a 10 gallon tank with a single veiltail betta?

I have been keeping betta fish for the last 6 years. The first I had for 5 years. My boyfriend won him on the boardwalk and it had this little itty bitty bowl which was terrible. So I moved him to a full sized fish bowl, which still was not nice since there was no filtration. Finally, I got him a filtered 1 gallon tank. After he died, I got a new one, but only had him for about 2-3 months and he passed away even though the tank was normal. I now have my third which I have had since October 2010. He's very healthy, and very swimmy, but my tank has a crack that in three weeks went from 1/2 inch to about 4 inches now. Obviously I need a new tank. I would like to upgrade him to a 10 gallong tank, but that's a lot of room for a single veiltail. I want a colorful tank to match his beautiful colors. I have done a lot of research, but the problem is that it never matched. There is always so much conflicting information that I can't get a straight answer. He is very docile and doesn't even attack his reflection. He's never really flared his fins in aggression either. I have heard dwarf gouramis are peaceful, but then I have also heard that they are aggressive nippers. Someone please help me and tell me what COLORFUL fish I can put in his 10 gallon I am planning to purchase? Thanks.