Below are some answers to help you:
I have used images mainly from Wikimedia Commons or freeimages.com (which used to be called sxc.hu). At times I have looked for artwork that is in the public domain due to the fact they were painted early last century. Some artwork is current but the artist has placed them on Wikimedia Commons (thank you!)
The purpose of the images is to give people an idea of what the symbols might mean, as well as jog some associations, like a Rorschach inkblot. In this way the images are used to help people learn about themselves, and are part of the site's self-teaching/healing tools.
This means that I was limited to the images I could use, since I didn't want to violate anyone's copyright. I also modified some royalty-free or public domain images.
If you know any royalty-free or public domain art or photos that would suit a particular symbol better than what I have found so far, please let me know here!
I have chosen to use the original handwritten symbols that M. E. Jones wrote onto the original cards. These handwritten symbols are helpfully included in Diana E. Roche's "The Sabian Symbols: A Screen of Prophecy", which is a very good place to further your interest in Sabian Symbol fundamentals.
Compared to the more poetic versions out there, I believe that the original and more sparse symbols allow more open interpretation for each person.
Radical ideas away from personality traits?
Since I know we can change as people while moving through life, and in fact we are a combination of repression and expression of various sides of ourselves (e.g. any of us could be any other of us given the right circumstances), then I prefer to view astrology as describing a journey, more than personality. Of course, it can be convenient to describe a symbol as a personality trait, or a personal preference, because that is how we have experienced it.
We can choose the emotional value of each journey (suffering, gratitude etc). We choose our responses and actions. So believing this, I can't reconcile the idea of our personalities as defined by our natal horoscope, by our sun sign etc. In a sense I ascribe to the Buddhist notions of who we are, which is that we are impermanent, as is everything else.
I believe the natal chart is a collection of things we wanted to learn in this life. Sometimes we make those lessons hard to learn, or they are simply hard due to deep subconscious patterns. We are free to make those lessons hard. But we will learn them.
So it's up to you: will you find the joy in learning, or will you suffer, or in between (the blessed middle path)? All paths still lead to, and beyond each lesson.
Trines, opposites, squares etc
So far, in my discussions with people, I find that the symbols themselves seem to be helpful enough.
Trines, opposites, squares and so on are extra mathematical layers that I don't feel this site needs to explore. I try to keep things as simple as possible. If it doesn't resonate for you, then it just doesn't. Going too deeply into the astro-maths, for me, would create for me the psychological effect of making facts try to fit the story. It is very human to do this. We do this most of the time. We may "find" patterns where there are none. And if we have invested time and effort into a belief, we find it hard to let that belief go (also exhibited by our hard-to-let-go deep-seated habits).
Since these astro-mathematical ideas are also conventions given to us (from where? from whom?) then I also acknowledge that they may be a guide, however I don't feel their truths resonate for me yet, so I can't offer any interpretation on them at this time.
In fact I feel that same way about most of the signs and houses (why are they divided like they are?) since over time, many cultures practised astrology completely differently and saw different images in the night sky.
What I do appreciate about astro-maths is the idea that the entire horoscope is an open system. Clearly each planet influences the others. There really are no closed-systems other than laboratories - everything has an effect on everything else.
So far I am only coming to terms with my own astronarrative, let alone comprehending how each element affects the other.
Why do I use the conventional signs then?
Purely for convenience. I am not trying to discover a new truth (many religions are battling that out, why join them?), however I believe an astronarrative can give you a perspective of your life that can be healing.
Good luck with your journey!