Hi Tiffany! Thanks for getting in touch and sorry for the trouble here with the featured images in your calendar.
I definitely see what you mean. Some of the images in the tooltip in Month View are nicely formatted and others are gigantic and overflow the container of the tooltip by a mile. That’s no good!
The first thing I noticed when digging around was that some of the images were true thumbnails and others were not. For example, check out this image:
http://www.fullcirclevenice.org/wp-content/uploads/2015/04/QiGongflyer-150×150.jpg
…and compare it to this image:
http://www.fullcirclevenice.org/wp-content/uploads/2015/05/OrmusSoundBath.jpg
Notice how the URL of the first one includes “-150×150” in the title and the second one does not.
That suggests to me that perhaps your theme is not always generating the a thumbnail for the images being uploaded. If it was, then we should be able to view the thumbnail for that second image here:
http://www.fullcirclevenice.org/wp-content/uploads/2015/05/OrmusSoundBath-150×150.jpg
…however, that returns a page not found.
Does the same thing happen when you use a default WordPress theme, like Twenty Fifteen? You would need to activate that theme and create new events to test, but you could do that on a subdirectory of your server so it doesn’t interfere with your live site, if you prefer.
Let’s start there and see what we find. 🙂
Cheers!
Geoff