SIGE - "reverse" image filter

Hello Viktor!
I've found the image filter option, and first I thought it would be quite useful for my use case. I suspected I could exclude specific images. But then I found out that the filter does include the chosen files.
What I would need is to exclude specific images from a gallery, like "show everything but main(.jpg) and intro(.jpg). At best I don't have to add the file extensions because in fact I don't know which kind of image (jpg png gif ... ) the user is choosing. 
Is that possible? Maybe I didn't find the correct option.
Thank you very much!
Chris