ok here what you do to make a png work...(don't use bmp.. and you can't just save a bmp as a png and expect different results, doesn't work like that....
first make your image with no backround at all... make the BG transparent, in PS this is known because the BG is checkered black and white.... then you make your complete image on the transparent BG.. you don't have to worry about colors so don't change it to 256.. leave it alone.. then you just save the png making sure the bg is still transparent... then load it into rco edit.. gimp and paint.net i know for sure doesn't handle alpha channel transparecy as well as photoshop.. but umm png works alot better than bmp now.. let me install PS again and ill fix the pic for you so you can see what to do