We are talking two different things when we talk about memory. There is storage memory, which is the size of your iPad's capacity (16GB, 32GB or 64GB). This memory is not fully available to the user because system software and such take up some of the space.
The other type of memory, RAM (random access memory) is the memory the iPad uses to load an app so it can run. The iPad1 got 256mb, while the iPad2 got 512mb. This RAM is the main reason why your iPad seems to slow or bog down. It has nothing to do with storage memory.
So, when your iPad starts to slow down, it's best to fully close out all the apps (via the multitasker - double click the home button and remove all the apps that show). Then, it's good to do a restart or a reset (or both). To do:
Restart: Hold down the power button until the power off slider appears. Slide it off. When the iPad finishes shutting down, hold down the power button again until the Apple logo appears.
Reset: Hold both the power and home buttons until the screen goes dark and the Apple logo then appears (the slide to unlock screen may or may not appear). Once the logo appears, release the buttons. After a time, your homescreen will appear. Please note that it may take some time for the Apple logo to appear or for your homescreen to appear (or both). This is normal. Eventually, the homescreen will appear.
Hopefully, that will make your iPad better able to view your pictures. Good luck and let us know how you get on.
Marilyn