for all who suffer from this ridiculous bug as I do ... today I discovered a workaround which works from wiithin Bryce itself.
All you need is a terrain (which usually you do). Then enter the Terrain Editor and goto the Picture Tab. From there click Load and choose the picture you want use in the Picture List (BTW the picture will load distorted ... but don’t worry). Then click on Copy and Cancel the Terrain Editor. Goto the Picture Editor and Paste it in any slot of your choice. Voila ... here it is.
Another problem is how to get a picture into one of the empty slots. Well, usually Bryce comes with the first two picture slots populated. I found out when you choose Save List and then Load List ... it appends the pictures to the existing ones. Doing so, you will be able to populate a bunch of slots which you may edit individually after.
Last but not least blame DAZ for doing such a bad job on this component and even worse that it hasn’t been fixed since months or years by know. Bought Bryce a couple of months ago ... but this bug is really a show stopper which prevented me to do any more serious work with it.