That is true, you can approach the way you play a chord differently and come up with a new sound. In the the end, they are still chords. Just alittle more extreme in there range. Although they are correctly spelled differently, they can be broken back into a reasonable chord even the feedback and harmonic ones. An example would be a 11th chord is the same note in the chord as sus4 extension. The aural range is limited to 12 notes, so however many combinations you can make of those notes is the limit of chords. Then again like you said, alot are not very pleasant to the ear. :) The one's that are pleasant are used more commonly.

On a extra note, chords are not only played harmonically, but melodically too. So those little riffs in songs are based on chords too. Like this.

G#b5 Amaj6 G#b5
E:-------------------------------|
B:-------------------------------|
G:-------------------------------|
D:-6-6-6-6-6---------------6-----|
A:-5-5-5-5-5--9p7-9p7------5-----|
E:-4-4-4-4-4----------9-5--4-----|