I'm not a fan of alliteration in names, but I reckon that's personal preference. If you like Mason, there's no reason not to use it! I don't think it's very common?
Here's some biblical suggestions for you:
Jonah
Noah (though this one is getting more popular!)
Levi (my DH LOVES this one. We're likely to use it if our baby's a boy.)
Eli or Elijah
Timothy (one of my faves. I know, it is quite common, but a traditional classic IMO.)
Samuel
Jacob
Isaac (some lovely variations of this one from other languages. I love Isaak, pronounced 'is-ah-c')

ETA: Sorry for the repeats - I took too long to post!