IF you are thinking catcher, the obvious choice is to call him Pudge (Fisk and Rodriguez), but you may not want to put it on the birth certificate.
You could also take a last name of a great backstop, Bench probably doesn't make a great first name. Fisk might work, but with a last name starting with S, it may be awkward. How about Carter (for Gary) Probably want to steer clear of Dickey. Campanella is interesting, but kind of long. Shorten it to Cam, Camp or Campy.
For first names, there's Josh (Gibson), Carlton (Fisk), Thurman (Munson), Elston (Howard),
You could go with Mickey, Cochrane, who Mickey Mantle was named afte,) and Tettleton. You could go with Mike (Piazza) Bill (Dickey), but they wouldn't stand out as baseball names.
For current catchers, you could consider Tek (Jason Varitek), but it's a little out there.
A few non-cather names you might want to consider - Brett, Aaron, Cobb, Tris, Robinson, Seaver, Gwynn, Cal (or Ripken), Jackson, Griffey, Palmer, Harmon, Kirby, or just Willie
And there's always Yogi.
Good luck!