Sounds like you are either missing some alpha channel data or have some data on tha alpha channel which is effecting things in the wrong way.
Images with areas of transparency usually have an 'alpha channel', which is used to map which areas will be transparent. So, on your emblem for example, you would have the three normal channels which make up the image (red, green, blue channels) plus another channel on which any part which is black will appear transparent when the image is used in the sim, and areas which are white will be opaque in the sim, and any shade in between black and white will have a varying degree of transparency depending on what shade of grey it is (usually there are 256 shades of grey readable from totally black, to totally white). So on your emblem, the alpha channel should look completely black apart from a white cleaver shape, so that only your cleaver shows up in the sim because the sim reads the areas of black as transparent.
So, to adjust this, you need to look on the 'channels' palette in your painting software and select or add an alpha channel and then work on that.
Chock