What are the pixel dimensions of your photos, the project settings, and the output settings?
How are you burning the disc?
DVDs are 720x480 pixels by nature. You can't increase the resolution of a DVD.
BluRay discs are 1920x1080 pixels, much higher resolution.
Meantime, be sure to check out this article from the FAQ library to the right of this forum.
Welcome to the forum.
As Steve points out, a DVD-Video is set in resolution, to 720 x 480 (for NTSC), in either Standard 4:3, or Widescreen 16:9. That is as good as it can get, and is not a limitation of PrE, but of the DVD-Video specs, which were written a long time ago.
The best that one can get is to play that DVD-Video on an up-rezzing DVD player, or most BD players, that also have up-rezzing, to an HD TV monitor. Those players have dedicated chips, JUST for up-rezzing.
Then, and per Peru Bob's questions, I attain the ultimate Still Images to DVD-Video, by doing my Scaling in Photoshop, and using either the Bicubic Sharper, or Bicubic Smoother Scaling algorithms. I Scale my Camera RAW Images to match my Project's Frame Size, and Crop, where necessary to match the Aspect Ratio of my Images, to the Aspect Ratio of the Project, i.e. if going to a 16:9 Widescreen, I will lose some pixels top and bottom, but I account for that, per my asesthetic.
Note: some PrE users insist that the Scaling in PrE is as good as Photoshop's, but my critical eyes point to using PS. Also, I do NOT use JPEG, which is a lossy, compressed format, and will Save_As PSD from Photoshop, for ultimate quality.
Good luck, and please let us know the pixel x pixel dimensions of your Images.