What computer operating system is your Premiere Elements 12 running? Have you updated 12 to 12.1 using an opened project's Help Menu/Updates? If not, please do that.
What are you creating - burn to DVD-VIDEO standard or widescreen on DVD disc or AVCHD format on DVD disc?
What are the pixel dimensions of the photos that you are importing into the project (also how many) and what are you (manually) or the project (automatically) setting for the project?
At this point, I am not sure if you are dealing with a matter of expectations not taking into consideration the resolution of the products or whether you are not getting the best possible from your workflow. So, we need to go through these details to determine the relevant factors.
1. DVD-VIDEO standard on DVD disc has a frame size of 720 x 480 (NTSC) and 720 x 576 (PAL).
2. DVD-VIDEO widescreen on DVD disc has a frame size of 720 x 480 (NTSC) and 720 x 576 (PAL) but a 16:9 flag stretches the video to display to 872 x 480 for NTSC and 1050 x 576 for PAL.
3. The AVCHD DVD can give you a product with 1920 x 1080 resolution. But the AVCHD DVD need a blu-ray player that supports AVCHD DVD for playback. Some multi media players are also said to support AVCHD on DVD.
What is in this slideshow, just photos or photos and videos? If video, what format and duration?
Please review and consider the above, supply details, and then we can decide what next based on the details of your reply.
Any questions or need clarification, please do not hesitate to ask.