So, here is my process.
I use Avery Design Pro software to easily make all my timeline pictures the same size. It is free, and I think they have it for various types of computer.
When I open it the first time, I chose to design the project from scratch.
Then I selected template 5214, as it makes a nice sized picture. (Each timeline picture is on a label.)
Then I use the buttons on the Left to add my text and images. I find the information and pictures usually by doing a google search... Leave the MASTER label blank, unless there is information you want on EVERY picture.
I often copy one label to another to make new timeline pictures. This helps them be consistent. I also rename the tab for the label (right click) and organize them in the order I will likely need them next year. For an AO Year, I have them organized by week. For Artists/Composers/Authors, I organize them alphabetically. For other things my kids ask for, I organize them chronologically. It works for me - but do whatever works for you. (I also have things in separate files, as our original single file got too large to work with easily.)
Finally, we print on regular paper and cut them out. If you were doing a whole year ahead, you could actually buy the Avery Labels... but as I'm only printing out a handful at a time (and often from more than one file), that would be a large waste. The scrap paper is used for protecting our timeline binders while gluing, or for colouring/drawing.
If I get people interested in my actual design-pro files (instead of the pdf's I've made available) let me know and I can look at adding it to the link above. Otherwise - I hope that some people take the plunge to making their own!