[photo id=xx]

This tag allows you to insert one photo of any size you want.

Options:
[photo id=46]

[photo id=46 album=22 size=M html=true link=true]

[random album=xx]

Same thing as above, except that the photo is chosen randomly from the whole gallery or from album.

[random]

[random album=123 size=M html=yes link=yes]

[cat=xx]

This tag inserts an album in the description, where xx is the album identifier.