Great idea for subject material. Let down firstly by strange black triangle border (I would think it would look better if there was a consistency in the texture and colour of the background across the whole frame. Let down further by very, very bad artifacts along all the edges of the triangle - there are whites, reds and greens all over the place.
mmh, there is something funny going on -- did you crop this triangle out of another picture? watch the settings of your USM if you used it and reduce contrast.