Yes, you can take a jpg/bmp/etc. into HDRShop, save it as a .hdr and use it in Bryce, but it will not have the lighting complexity that a real HDRI would have. I have done this myself since there are some sites that have jpgs in a panoranical format to wrap around a sphere perfectly. Works in a pinch if it a specific image that you want reflected.

In the link I have in the Forum header (HDRI's for Bryce 6), on that page near the bottom is a link to make a synthetic HDRI in Photoshop, although it uses just a simple process, you could use that to process a full image into a more realistic HDRI.

I would assume you could do a similar process in HDRShop, although I have not yet had time to look that over in detail

Contact Me | Gallery | Freestuff | IMDB Credits | Personal Site
"I want to be what I was when I wanted to be what I am now"