I have to say so far I have hit this nose-on since I only have 69 or so pictures that aren't mine. I have used replacements for those pictures I couldn't get (looking at you white monarch), that my phone had problems getting such as the meteors, missing photos, etc.
In some cases it will seem that my pics are repeats of others for different items but that is okay if it does the job. And some of the other pictures that I have used non-personal pictures for I can also eventually get pictures although they won't be related to when I marked the goal off. But that is all the fun in collecting experiences is weaving them all together for a bigger and better story.