I’m having a similar issue where images used in my testimonials slider are being rendered at random sizes. They are all inserted as 150×150, but they come up all different and inconsistent sizes.
Initially, when I first tried inserting the images, as the original poster, it would be this huge image (no matter the size of the inserted image) centered above the testimonial.
In order to get the image to be next to it, I used the shortcode for a table and put an image on a column next to the text. This may be related to the variable sizing.
When I have more text, the image gets smaller/tinier. When I have less text, the image gets really big.
I turned off the responsive function, and it was the same.
What is the best method to get an image to appear next to a testimonial?