Here is how you convert a PNG image from a PIL (the Python Image Library format) object to a wxPython Image (or Bitmap) while keeping the alpha transparency layer.
Why convert? so you can use that bitmap to draw onto something like FloatCanvas.
[python]
from PIL import Image
import wx
pilImage = Image.open('my.png')
image = wx.EmptyImage(pilImage.size[0],pilImage.size[1])
image.setData(pil.convert("RGB").tostring())
image.setAlphaData(pil.convert("RGBA").tostring()[3::4]
## use the wx.Image or convert it to wx.Bitmap
bitmap = wx.BitmapFromImage(image)
[/python]
Thats it. I hope that helps future googlers.