fileTooBig ... that means the file is too big, not the picture.

Look at the size of the file, it must be under 100k. Your picture could be 1000x1000 pixels, as long as it is under 100k. (but please keep them 640-pixels wide or less to fit nicely on a web page).

To reduce the size, save the picture with more compression. Around 70-80 percent is good. That 20-30% if using some tools that measure it backwards.