Itunes asks you for the folder where your pics are located. i believe it sifts through ur my pictures folder. and you are free to pick as many folders as you want.
The 3.0 firmware lets you sync different content with different computers. Music, Movies, TV Shows, Podcasts, Photos, Info, and Applications can each be synced with different computers if you wished. On a Windows system, you can sync photos through iTunes from Adobe Photoshop Elements versions 3.0-5.0, Adobe Photoshop Album 2.0 or later, or a folder from Windows Explorer, as documented by this. If you have folders within the folder of choice you can sync more than one folder of photos. For example if you have selected to sync pictures from the My Pictures/Pictures folder, and you have folders within My Pictures, you will have the option to sync selected folders rather than the individual images in that directory. Hope this made things a little more clearer.
You can sync different content from different computers with previous firmwares also. I have 2.1 and have my music, apps, and videos synced with my pc while contacts, calendars and photos are synced with my mac. I have been doing this since the first ipod touch firmware.