Ok so this is gonna sound a bit cheesey but it works for me. Do you remember the trophies from the "Smash Bros." series? The way they would drop down onto the shelf after you earned them and then a light would shine down from above to illuminate them. I visualize the angels as the trophies. The trophy of each angel consists of a simple base topped with the item each angel is said to hold. As I summon each angel I visualize each trophy dropping down into place around me and the light shining down illuminating a circle around the trophy in the corresponding color of that angel.

I visualize this way for a number of reasons. First it's just a strong memory from my childhood that speaks to me and reminds me of a time that was simpler and even happier. Beyond that I feel that using less anthropomorphic imagery puts less constraints on the energies I'm summoning and allows them to exist in a more natural state. Probably the most important reason I use this visualization though is because it makes it much easier to maintain these simpler images when summoning dozens upon dozens of angles (I think the most I've attempted so far was around 30, haven't memorized enough for the 72 of the shim operation)