orientation is a bitfield, the flags of which determine how a sprite is drawn. Here are the known bits and what they do. There may be others:
1 - translucency level one (66% opacity).
2 - scaling on 320-200 coordinates. This is implicitly applied to all CON screen drawing commands, but including it in your bitfields is recommended for clarity and portability of your code.
4 - used to invert Y coordinates. Combine this bit with an angle of 1024 (using rotatesprite) and the tile will appear to have inverted X coordinates. If you want inversion for both the X and Y coordinates, simply set the angle (again, with rotatesprite) to 1024 and do not use this bit.
8 - causes the sprite to be not affected by the screen size (using the + or - commands). This is usefull, for example, when displaying a status bar.
16 - forces the center of the sprite you're drawing to its top-left if set. It also ignores the x-y offset of the tile.
32 - is translucency level two (33% opacity). It won't work if 1 is not set.
64 - forces masking off if set. It discards translucency too.
128 - "permanent" tile (deprecated).
256 - Align to the left (widescreen support)
512 - Align to the right (widescreen support)
1024 - Stretch to screen resolution (distorts aspect ratio; this is the behavior of rotatesprite prior to widescreen awareness)
As with cstat, the bit values can be added together and used in combination. For example, orientation 33 (32+1) is transparency level two, and orientation 5 (4+1) is transparency level one with inverted Y coordinates.