Photos have never (to my memory) been a part of the iCloud Backup. While they are stored in iCloud (if the feature is enabled) they are separate from the backup.
I honestly can't remember how they were backed up in iOS 5, but here are a few things that might help you.
If the photos are stored entirely on the iPad itself, You can try a couple things.
1) Jupiter 7 mentioned using File Explorer on the PC. When the iPad is plugged in it should show up as a USB Drive, and show your images in a folder directory similar to a digital camera's SD card. Unfortunately, this usually only includes photos take in the iPad itself, and not those added by other means.
2) More reliable and flexible, you can use third party apps like PhotoSync to copy your photos from the iPad to PC over your network. If you purchased/downloaded the app before, it might download a version compatible with your older OS. However the current version is not compatible with iOS 5. With some searching, you might find an app that is.
3) The PC app iMazing is capable of copying just about anythng from your iPad to you PC, and performing other backup/syncing chores. I don't know if it will work with you older iPad, but I believe it still has a free trial version that you can make sure works before purchasing. This is probably the most flexible and likely to work option, but since I've never used it I can't guarantee. Some other members are more familiar with the app, and might even be able to tell you if it still supports older iPads and OS versions.
4) The iTunes app for the PC is what was used to sync photos early on. I haven't used in in a long time, so I can't say it will still work on the older iPad for sure. I caution you to be careful if you initiate sync in iTunes. Read any dialogs closely and make sure you don't accidentally delete the existing library on the iPad.
If you iPad has synced Photos to iCloud.
1) You may be able to access them by going to iCloud.com and signing in with your Apple ID. The copy mechanism isn't designed for massive photo transfers, so it would be slow going.
2) I'm not sure why I numbered the second list, I can't think of anything else.
