The Flowers demo stacks shows the multimedia capabilities of MoStacks (well, only two medias so far, text and pictures). There is a basic field type Picture. Such a field is able to hold and display a picture, either sized to fit the size of the field, full-sized within the field (with scrollbars) or in a full-screen picture viewer.
Picture fields are fields like any other; you can e.g. put more than one onto a card.