]Are you saying you want to show transparency while in textured view or do you need something in addition to this.
If so then it does it fine while in Textured view mode with GLSL selected.
The cube with a transparent material and a plane with an image applied
test-1.blend (60.2 KB) transparent.blend (67.8 KB)
You don’t seem to have GLSL enabled. I have turned it on in your file as well as attaching the blend for my previous image.