It appears Superlab doesn’t support GIF format files. I think that support for GIF-based animation might be a useful way to allow users to specify certain visual stimulus manipulations. That is, based on the parameters in the GIF, sequences of visual stimuli could run in parallel with the flow of the Superlab scenario. Superlab could disallow certain GIF options, for example, delays that are not an integral multiple of the current frame rate.
Once GIFs are supported, you could also treat a GIF as an archive of frames and frame-sequences, similar in some ways to the stimulus list concept.
You would also have to be able to terminate the playing of a GIF prematurely such as at the end of a trial or when a response is received.
And, if you really wanted to get fancy, Superlab could make changes in the screen while a GIF is running, for example, other images or even other GIFs.
There is also the possibility of Superlab using GIF extensions such as commands embedded in comments, for things like conditional looping or branching based on variables and/or responses. But that might be going too far.
There are readily-accessible, free tools out there for putting animated GIFs together, such as gifsicle.