Wes Moore or Raphael Warnock.
Agreed.
Ruben Gallego also makes sense. A white woman from the Midwest would be balanced by a man of color from a different region.
Wes Moore would cause few headaches, although he wouldn't help with governing or swing any useful region.
Most Democratic running mates have been Senators, and it makes sense. The party prefers a strong federal government, Senators are statewide officeholders so they seem qualified, and Senators are supposed to be familiar with national issues so it should avoid major gaffes.
Hakeem Jeffries would provide balance and help govern, but I'm not sure what swing voters he'd appeal to.
Fetterman would double-up strength in rust-belt swing states. The main knock is that it would be a ticket with two white people.