Are you using BitmapSample? Have you defined the Bitmap Globally, as this can be reused, as opposed to keeping on grabbing memory allocation if used locally.
How big, in pixel terms are the images?
I've put in place a recycle and a try, if my image loading fails, then it loads a smaller (both pixel and memory size) version of the images.. This seems to keep things limited to a sensible level.
Are you using B4A ver 2.7?