Spider-Man Signal Civil War Concept Art Features Iron Man
We see that originally they had the idea of using an image of Iron Man, since Tony Stark provided Peter Parker with the tech.
"Swing by the tower. Got some new upgrades you should see," Iron Man's message to Spider-Man says.
It's unknown exactly why Iron Man was cut from the scene, but it would have made perfect sense as Robert Downey Jr. is set to be featured in Spider-Man: Homecoming. Perhaps they wanted to keep the scene focused more on Peter than anything else or wanted to keep a new Spider-Man costume a surprise.
Perception added about their artwork:
Within a very tight turnaround (days, not weeks) the Perception team developed a range of visual concepts displaying the Spidey Signal. Perception tinkered with several aesthetics and purposes— from tactical X-rays to playful social media. Presenting a wide range of concepts turbocharged the process. Kevin Feige and (Civil War directors) Joe & Anthony Russo quickly focused on an ideal approach. Minor tweaks were made, and the elements were integrated into the final film before we knew it.