I did try earlier (for a good hour this morning, while researching the topic) and couldn't even get WoW to recognize the name
SetPortraitToTexture or
SetPortraitTexture. Want to provide a working example, please? I think if they did work, which they might outside my oUF, but I couldn't convince them to work in oUF), then the resulting image would probably be flat, leading to the look like in SquidFrame picture.