There is most certainly a way.
But it's not clear exactly what you're asking.
Are you saying you have a song and a slideshow and you want to make them both the same length?
There is no automatic way -- but here's a method many have used.
Create your slideshow (make sure your photos are no larger than 1000x750 pixels!) and then use Share/Personal Computer/AVI to output the sequence as a DV-AVI.
Open a new project and place your music on the Soundtrack track.
Use Get Media to add your slideshow AVI to the project and place it on the timeline, above the music track.
Select the Time Stretch tool along the top of the Timeline panel and "stretch" the AVI until it is the same length as the music track.
Given that in Photoshop Elements SlideShow Editor there is a Fit Audio to Slides feature for the Filmstrip and audio bar content, but not so for Premiere Elements.
OK, so you find yourself creating your slideshow in Premiere Elements alone, in this case, Premiere Elements 8.0.1.
The first bit of information that I would like is the actual length of the photo content on video track 1 and the actual length of the audio clip involved (specified as audio 1, soundtrack, or narration clip).
You suggest the intervention of the DV AVI version of the Timeline photos for reimport and you conclude:
"Select the Time Stretch tool along the top of the Timeline panel and "stretch" the AVI until it is the same length as the music track".
One of the problems that I have with that DV AVI route is that, once you get the DV AVI version of the original photos back to the Timeline, any significant editing opportunities are lost at that point. A lot to be considered. Since Premiere Elements 8.0.1 seems to be involved here, might not one avenue to explore be:
a. selecting all the photos on video track 1, right clicking anywhere in the highlight, selecting Time Stretch, and setting an "increased" duration for each of the selected photos so that the total of the photos with increased duration = length of the soundtrack. That is doable in version 8, but was not in version 7.
b. use of Smart Sound Music that comes with the program.
Just some thoughts for a question that I might have answered No as written.
All good points, Tony.
The AVI/Time Stretch method is by no means the only solution. It's just a simple one -- and with the limitations any simple solution would have.