Yesterday Merlin's Keep uploaded 12 new S4 promo pics to their website, mostly known motives. Plus there's one MedRes pic of Morgana from episode 04.05 I found on a German website that looks new to me.
A few days ago Merlin's Keep also added pics of the Knights' Gay Times photo shooting (incl some outtakes) to their site, some were HiRes, some MedRes. Here are some of the MedRes pics in a higher (HiRes) resolution.