What you are asking specifically to do is not possible. It's also possible there may be a confusion in terms here.
Photo Stream is intended to upload from the device which took the picture, in order for it to be distributed to all of your devices. Pictures are only uploaded from the point where you turn the service on, going forward, and are only stored for up to 30 days. It is not a permanent storage solution. Therefore uploading thousands of photos from your Camera Roll to Photo Stream would not really do you any good, even if it was possible (which it is not).
iCloud Photo Library, which has now officially launched with the release of Mac OS X 10.10.3 and iOS 8.3, is intended to be a permanent storage solution. Original files are uploaded to iCloud Photo Library and each device can choose to download original files or previews (which are intended to save space). Your entire photo library is then available from any iOS device, Mac, Windows (with iCloud support installed) or the web. Note that your iPod touch (4th generation) cannot upgrade past iOS 6.1.6, and therefore cannot use iCloud Photo Library.
Since you are looking for a permanent storage option, given the iOS limitations of your device, the best solution is to physically attach it to a computer and import the photos into the program of your choice. If that's a Mac running 10.10.3, you can use Photos and enable iCloud Photo Library. Once you have a newer device running iOS 8.3 or later, you can then enable iCloud Photo Library on the device to view all of your pictures.