Creating video from sequence or pictures
A lot of users want to transform their photos or pictures to a single video that shows the pictures in a sequence. You can find plenty of presentation programs with which users can prepare MP4 videos that are basically sequences of pictures or photos with music playing in background, similar to what you can see on Youtube. If you are interested in this, you can search on internet for "image to video/slideshow", "how to create slideshow" or "photo to movie slideshow software" for additional software picks.
In situations when users want to create a video from large number many pictures and will need a software that combine thousands .jpg photos to create a time-lapse .mp4 video, ideally with a batch import support so these sequences are created in one go. Before this process it is recommended to batch resize all photos to the same size i.e., to fit all newly created video dimensions to 1980 pixels / 1080 pixels for Full HD video.
Any of the programs listed below, should be capable of this picture to video conversion and you may find dozens other programs for all platforms on Internet. Even some online converters support this, for example Picovico. Also, there are apps for iPhones or Android phones designed exactly for photo to video conversion, so users can share pictures from their phone cameras.
Showing pictures during audio playback
MPEG-4 (.mp4) is a container for multimedia content, including video or audio and may also contain images which can be shown during playback. This function is usually needed when you want some pictures to be shown during audio playback. Some media players allows users to embed picture to their audio files, but it would not make sense for videos.