Its nothing to do with the loadimage flags. Its to do with your Graphics command. If you are in windowed then you use the window bit depth, If you are in full screen then when you open the screen you select the bitdepth.
Graphics( width,height,depth=0), so try
Graphics( width,height,32) in release mode
Graphics( width,height,depth=0), so try
Graphics( width,height,32) in release mode