i cant upload my custom portraits-help!

[ammama]

i've finnally gotten a wide selection of portraits i like, but none of them are the rite size, and they dont register on the game anyway. what size do the big and small portraits have to be, and what image type (btmp or jpeg etc.). I heard sumthing about having to name them with a specific amount of letters ending in S or L depending on the size. can sum1 please help.