1.Drag & Drop to open image files: It can be a good facility to be able to just drag and drop image files to the Ultraiso window to open them. The left box (where the cd title is) or the toolbar could be a good location for dropping the file to be opened.
2.Password Dialogue Integration with Save Dialogue: You can Integrate the Password and Save dialogues together and make the Password section (that would be under the file name) active by using a check-box:
It can facilitate the process of making password protected files or regular ones through avoiding the alternative way of doing this: Options>Compression>Password Protection --> clearing check box each time you change your mind about setting a password. So: just transfer a copy of that Options box to save dialogue box (make sure to include all AES/Split/Method options)
3.Context menu Mount: Currently (maybe because the extension are associated with other programs) I don't find Ultraiso context menu when right clicking supported files. So: Add context menu for the supported files (having the option to include an icon for it or have a simple text menu item)