They don't cache images (of Pokestops) client-side. This has got to be one of the bigger inefficiencies of this client. Aggressive client-side caching can relieve a lot of load on the server.
Everyone I talk to who's also played Ingress sees history repeating itself. They've experienced the same bugs, lack of communication, shutting down services making the game better instead of improving said game and whatnot.
I really, really wish Niantic fixes its technical, management and communication problems. The game has so much potential but at this point I lost almost all hope they'll be able fully exploit it.
The graph they showed was of spatial queries. That's not going to be affected by lookups of images for pokestops.