Since all of the pictures I used in describing two weeks of this year were taken by myself then no, I didnt experience any difficulties in picking them out. It was rather a case of when did I find myself unoccupied or even slightly tired of doing something for a while (gap of inactivity) and than decided to memorize it as a moment of my week. The pictures are not a cypher to me since I have a certain connection behind them or even a story somewhat. There are also pictures that for me even describe an adventure of sorts and that might be cypherlike.
If you put the pictures beside each other, one might come up with a story. It might even describe a whole timeline albeit a boring and mundane one. My story is mostly describing work, locations and feelings towards something.
Picking pictures to describe something is easier for me if I take the pictures themselves. I dont photograph a lot, so its not one of my hobbies. It is easy to understand though, why people share a lot of pictures online and in social networks. Easier than typing numerous words in succession to explain a situation or make a point..
Is a picture worth a thousand words? Yes, but mostly different words to different people.