From my experience with Delta types, I often find that their appearance is composed of two elements: curious/silly eyes and a pinched mouth. I'll get more into this in a bit.
The specific images above are of TeSi and SiTe types, which are the more grounded half of this quadrant. I've heard people describe high-Si/Te Deltas as very 'adult-like' and bureaucratic, and this precisely fits my observation too.
If we actually look at politics, news anchors, trivia games, etc -- we find this same appearance continually:
For the Delta types, like the Alpha types, the eyes are not "intense" or "hypnotic" like those of the Betas. Instead, their eyes look more silly, naive and a little dazed. It's hard to describe it in words, but here is an example of the Ne/Si eye appearance:
They look a bit alert, wide, yet somewhat scattered/unfocused. The area around the eye is not pulled sharply like the eyes of Ni/Se. For the Ni/Se types, the eyes themselves look more focused, and the area around the eyes is not at all relaxed, but instead very stretched and sharp. I believe this is due to the two having different perceptive focus. The more casual disposition of Ne toward details in the environment gives it a more free-reigning quality. They are also more prone to toggle about and glance at different areas. The more sensational and direct disposition of Se toward the environment gives it a more intense and well connected and locked-on to specific qualities.
Now, the mouth of the Delta types is like the mouth of the Gamma types: Te/Fi. It has that pinched quality near the nose, and is prone to make a lot of asymmetrical facial expressions when talking.
Have any of you seen a similar trend with Deltas?