You can change how the photo slideshow feature works within the normal Settings area.. Select Settings from the iPod Touch desktop. Once in there go to the third section down and select Photos, which is under Video and above Mail, Contacts, Calendars. Each of these Settings options are under the heading Slideshow. The top option is for how long you want the photo slideshow to play each photo for. It is set at a default of three seconds, which is fairly adequate. You only really want to go one second up or down, otherwise the image will be too short to comprehend or will be so slow that it distracts the viewer.
Below that is the option to set what transition you want between slideshow images, which is currently set as Dissolve. You have a few others at your availability, but if you want it to remain unnoticed you may just want to stick with dissolve. The next two options are Repeat and Shuffle, which you can set to on or off. Repeat may not be a good one unless you think people will want to look over your iPod Touch Photos over and over again. Shuffle is alright as long as you did not arrange them in a specific order ahead of time.