Emm... Thank you for kind words. But I just can't understand, what do you ask... I send my coats to Howrse in PNG format, it supports transparency. Maybe these transparent parts won't be seen on the game background, but the darker background will suit perfectly. So you should use Helios' Ray or Harmony Pack to get the best look.
If you asked something different, try again)) I'm not so good in English, maybe you should use easier language.
When I draw, I tend to have problems with transparency. For example I made a dragon horse with a really long white mane and tail not long back, but on a white background, you could barely see the mane. On a black background, the black came through the mane in splodges and looked awful. I've just never figured out how to fix this, and you seem to not have a problem with it.