It'd be good if your budget allows for two subs, such as EP500s or EP350s, but placement to minimize the effect of room modes is desirable to get the most out of them. This generally means the mid-point of the front and back walls or the mid-points of opposite side walls or in diagonally opposite corners.
Looking at your room pictures, there's a possibility that diagonally opposite corners would work well. The front right corner seems to have enough room, and if room can be made in the left back corner(the chair is blocking the view), that should be an effective setup.
