There is no limit for that I think. I am 857 itlv atm and items I got are 835-840.
I got one 855 from bg and also one legendary from Bg so I think there is no limit just poor rewards for pvp
In last two days all items bg dropped me were at least 15 itlv lower then mine. Last 30 bgs and a single item that I can use.
There are pvp and pve players and now pvp is useless for gearing.
Is it just bad luck or every pvp player feel the same?