Here's an example of the aura that I currently use.

I want to change the freezing_circle.bmp to hearts like from Dancer's Fortune's Kiss or Wink of Charm. (directly from the sprite files/.grf if possible?)
I want to change the whitelight.tga to sakura petals. I've had no luck finding anything like either in any aura packs, and I have no idea how I should get started.
I do have a couple GRF tools and possibly a sprite viewer. Where do I go from here?
Edit: A friend helped me get the heart effect and some petals, thank you :>

Although, I am still rather curious about what programs other people use to edit .tga files and the like.