Images cover form

Hello. I'm trying different images for the cover of the form. The problem is that I not find a way to erase from the designer charged images that no longer serve me.
I have to make many forms and can be a mess have a lot of images in the upload form cover screen. Thanks in advance.

Unfortunately there is no provision to remove the uploaded image in the designer, I have submitted a feature request to our developers for this facility. We will let you know once its made available