Postmarked that date, didn't make it here until 07/2014... probably since it came from Kinshasa.

Letter 1:
Front of envelope
Photo (contents)

Letter 2:
Front of envelope
Shape/front
Shape/back

Letter 3:
Front of envelope
Photo (contents)
Photo back

Comments: The letter 1 photo is interesting. Downtown Tucson, our favorite former bank. Taken standing 
across the street from the cathedral. Early some morning (sunrise?) at least 15 years ago. Is it a 
"from film photo" or a printed scan?
Any chance you could read what is on the parking garage bill board? The other photo is sunset, I don't know where.

Looks like the pic in submission 06/14/2014,letter no. 1 is a few years old, but it was taken a few feet from 

27 E Corral, Tucson, 85701 (https://www.google.com/maps/@32.219135,-110.970374,3a,75y,90t/data=!3m4!1e1!3m2!1sXJufr4KPWABw7db5_xyQ3g!2e0?hl=en)

The photo shows the rising sun's reflection from one of the facets of the UniSource Energy Building on Church Av.
Very unusual "solid light" effect in the reflection, but note the foggy haze to the west behind the Court House and the 
parking structure. There may have been some actual humidity in the air that morning.

1: please measure the stamps distance and the ink stamp degrees.

2: Letter 2 shape/back is orion's belt.

3: The image is from Don Relyea's "Super Collider"

4: letter 3 is labeled letter 2 and vice versa! look at the stars... man! That son was totally right about you!

SUGGESTION: Don Relyea's site only get's 7000 hits per year. I would ask him for an IP list of the last year. 
If you get that I can track who this came from.

Letter 2, shape front. http://www.donrelyea.com/lsystem/algorithmic_art.htm

It's an algorithmic art project by a guy named Don Relyea.  The above link is his website.  
The artwork that the image came from is called 'Super Collider'  It uses images of a atom 
smasher to generate artwork based on mathematical equations.

The photo on the first letter is from Tucson, Arizona (you probably knew that already). The big 
building in the middle is One South Church, formerly known as Unisource energy tower.

The picture is old though. It's taken about at crossroads of S Stone Ave and Ochoa St. The tower 
was built in -88; judging from the cars & lightposts in the image, early 90s would be a good guess for the date.

One could propably find the exact date by digging into Tucsons rezoning and renovations archives

I feel a little dumb for not realizing this sooner, but this is the same picture that is part of the 5/1/1997 ad.