I find it funny that after 3 responses I'm the first to ask how you got the photos onto the iPod. Did you sync them through iTunes or did you save pictures from websites, take screenshots, or capture them with the camera if you have the 4th gen touch? If you added the pictures through iTunes, you can only remove them by limiting or disabling your options in the Photos tab. If you saved these pictures while browsing the internet, by taking a screenshot, or shooting them with the camera, you can navigate to the Photos app, tab on one of the images, and then the Trash icon in the bottom right.