Ryan Petrich's Grabby tweak has been updated with a bunch of new features, making it a much more well rounded tweak than the initial release. With version 0.2, downloadable now on Petrich's personal beta repo, you can have up to five apps assigned to the Lock screen camera grabber at once.
But, of course, that's not all. This latest version lends the ability to mix and match the icons featured on the camera grabber, along with the ability to display the actual app icons themselves. The tweak is still in beta, but if you were hesitant to try it out the first time, you may want to considering trying it out now.