Hey Josh,

If the first pic in a Steemit post has parenthesis in its filename, the pic will not show as a thumbnail in the feed. For example, photo(123).jpg will not show as a thumbnail.

The reason for this is, steemit User Interface uses the background-image attribute to display a thumbnail image in the feed lists. You can learn about that on any site that teaches HTML, one is https://www.w3schools.com/cssref/pr_background-image.asp

So the code for this attribute is
background-image: url("paper.gif");
for example. And if the filename of the image, paper.gif in this example, contained a close parentheses ) then that causes browsers to interpret the close parenthesis in the filename as the end of the background-image parameter, so the filename is truncated into something that does not exist.

Feel free to experiment and see what I mean. Next time you see this issue, check if there are parenthesis in the filename of the first pic. If so, rename it to something without parenthesis and it will display correctly.

I've been telling people about this issue for months. See here: https://steemit.com/steemit/@auroralyrayoga/why-aren-t-my-thumbnail-images-showing-up

Maybe one day steemit will fix this bug :-) Have a great weekend!