PNG

PNG, or Portable Network Graphics, is an image format often used in video games. An explanation of the PNG file format can be found on Wikipedia: Portable Network Graphics

In DBPF versions 1.0/1.1, the Type ID is 0x856DDBAC.

In DBPF versions 2.0/3.0, the Type ID is 0x2F7D0004.

SimCity 4

SimCity 4 uses PNG images for a variety of purposes. They are used for screenshots taken in-game, but most commonly are used as the format used for user interface (UI) elements.

PNG Icons

PNG icons are a specific subset of PNGs which are attached to a ploppable lot and shown in user interface menus. Lot icons additionally have a Group ID of 0x6A386D26. These images are 176x44px in size and consists of a strip of 4 44x44px icons, one icon each for when the item is locked, unlocked, currently selected, and highlighted. An icon is attached to a lot through its Instance ID. A lot references its icon through the Item Icon property.

Lot Preview

Ploppable lots may also include a PNG preview of the lot inside embedded in the DBPF file. These images are not used by the game - they are automatically generated by the Lot Editor and were intended for use when sharing on the old official Maxis custom content exchange As such these previews are no longer useful and may be safely removed from a DBPF file without consequence.

SimCity

SimCity (2013) uses it to store user interface elements in DBPF files.