Center:
Eye - This isn't a reference to the Illuminati Cult, it actually means that he's able to watch the past, the present, and the future, that's why the eye is in the middle of everything.
Small Heads - Represent his ability to be dead, old, young, a baby, and an adult at the same time, because of time travel.
Left Side:
Clock Wheels - Represent the internal mechanism of a clock, obviously a reference to time.
Airplane & Angel - This could be a reference to the conversation that Jenny was having with the preacher in RDR1, about how "soon people would be able to fly", but then the preacher corrects her by saying "No, only angels can fly, Jenny". In other words, the introduction of airplanes.
Soldiers - Represent the First World War, you can tell that those are soldiers by looking at the silhouettes of their uniforms.
New York City - We can appreciate a 1930s version of New York City, the first recognizable landmark is the Chrysler Building, completed in 1930.
Blimp - A normal blimp, probably one from the 1920s or 1930s.
Factory Chimneys - A clear reference to the huge amount of contamination created by big cities like Saint Denis.
Boat - It represents the introduction of luxurious Cruise Ships from the 1970s-1980s for vacationing travelers, back when airlines were taking over the travelling industry.
Nuclear Explosion & Symbols - The nuclear mushroom and the symbol to the left represent the upcoming Atomic War, while the DNA symbol represents the important genetic discoveries that were made in the 1910s-Actuality.
Nuclear Weapon: There's a drawing of a rocket flying above some small houses, most likely a military camp, this is connected with the previous point.
Space - Represents another upcoming conflict, the one between USA and the Soviet Union, in which both countries were basically fighting about who had better rockets lol.
Right Side:
Cowboy On Wagon - An obvious representation of the Old West (RDR's timeline).
Portals - This part of the mural shows us what type of time traveling abilities he uses to jump from one period in time to another.
Ship - This is a Viking ship, a reference to the first Viking explorers that made trips to American territories, some of them tried to colonize said territories.
Meteor - It's safe to say that this is a reference to the crater that we can find near Doverhill, Ambarino.
Star - It might be a Biblical reference to the Star of Bethlehem.
Egypt - This entire section is dedicated to Egyptian history, we can even notice some slaves lifting a structure at the bottom.
Flying UFO - I can't figure out what that thing is yet.
Conclusion:
The right side of the mural is a prediction of what's coming in like 70 years or more, while the left side is a compilation of important historical events. It is unknown to me why ancient people (or time travelers) chose to left warnings about the future in the form of rock carvings, but Francis Sinclair's plan probably heads towards alerting people from his time.
Side Note:
Redheads in RDR can be descendants of Kraff or whatever that is in that universe, while in GTA we haven't seen redheads with special abilities, only Chris Formage.