You should be able to modify the SD.Email.Monitor project to strip out the images based on their filename while it runs through the processing of e-mail attachments.
You will make the modification in the ProcessMessage model inside SD.Email.Monitor. Once you open this model scroll all the way to the top right of the screen. Here is a sample of the modification using a 'Matches Rule' component to list the specific filenames I'm looking for. If the EachAttachment.Filename variable matches then it routes back to the 'For Each Attachment' component. Anything that doesn't match routes to the Add Attachment component.
Once you've made the modification and added the list of files you don't wish to have saved as attachments simply save & publish the project.