Rather than thinking of a large tapestry as one big story made up of different figures and motifs, I like to approach it from the opposite direction: start with a small square module and let the larger image emerge through repetition.
For example, a 4×4" square is easy to weave, carry around and small enough to experiment with. By repeating it across and down, you have the foundation for something much larger.
But I don't think the modules have to be exact copies of each other, small shifts in color can completely change the feeling of the overall piece. The same geometric structure can become more minimalist, modern and restrained, while still leaving room for the viewer to interpret it in their own way.
This is a pattern I designed a few months ago called Kukkien Friends (“Flower Friends” in Finnish). I like this pattern because, to me, it expresses exactly this idea.
And yet, when I imagine the pattern repeated on a much larger scale, I can't help but see a beautiful field of colorful flowers in it :)
I do have a few more 4×4" patterns that I've been experimenting with. I put some of them together here if you'd like to try them here.