Pictures and other media are parts of their own, kept as they are, in
ppt/media/. A slide refers to one through a relationship, so two slides can
share the same picture.
Pictures
A p:pic holds p:blipFill/a:blip. The attribute
r:embed names a relationship to a part in the package, and
r:link a relationship to an external file. Pictures are usually PNG or JPEG,
and also GIF, EMF, WMF, TIFF or SVG. a:blip can also fill a shape.
A file may also have a thumbnail, docProps/thumbnail.jpeg.
Audio and video
A media file is a p:pic whose non-visual properties hold an
a:audioFile or a:videoFile with a relationship to the media
part, and the picture shown before it plays. Media can be embedded or linked.
Charts and diagrams
A chart is a c:chart reference to a part in ppt/charts/,
usually with an embedded spreadsheet of its data in ppt/embeddings/. A
SmartArt diagram is held in several parts in ppt/diagrams/: its data, layout,
colours and style, and sometimes a drawing part with the shapes already laid out.
Embedded objects
An OLE object is a p:oleObj in a graphic frame, with a relationship to a
part in ppt/embeddings/, and a picture of the object to show. Embedded Office
documents are kept as .xlsx, .docx or similar files, and older
OLE objects as .bin compound files.