Been busy hacking away. Took a few days, but I finally got FM to use DevIL to load an external image.
First, you will need the filter: UberD_b2_DevIL.rar
PC/Win only, RGB 8-bit. Drop that into your filter directory and fire up your host. Should show up as Filter > Tech Slop > Uber Displace b2.
Bear in mind that this has less bells-n-whistles than b1 (which didn't have very many to begin with). Always uses Stretch to Fit and bilinear interpolation. Haven't gotten into the strings yet so the Load D-Map dialog might start you off in an odd directory.
You will need DevIL.dll in order for Uber Displace b2 to work. This provides the image loading functionality that I've been craving for so long. I have mine in my filter directory and it loads fine. You should be able to toss this into your System32 dir, but I haven't tested that. DevIL Download
I currently have it set for these formats: JPG, BMP, PSD, and TGA. Those are the formats that I use the most (but hopefully not BMP anymore), so those are what I put in.
For PSD D-Maps, make sure that you have Image Preview turned on. You might also have to have Maximize Backwards turned on as well, but I can't say for sure. And save in RGB mode... I have quite a few PSD files in Lab mode and DevIL didn't seem to like that. Heh.
Also, if there is transparency in the file (PSD or TGA), I think it fills with pure white. But, again, I can't say for sure.