I found a way to change the type of image, via blockreinsurance.tpl file from your theme module folder, from .jpg to .png or anything else you need without modifying .php file
in the blockreinsurance.tpl file on line 30 you have something like this
src="{$link->getMediaLink("`$module_dir`img/`$info.file_name|escape:'htmlall':'UTF-8'`")}"
you just change it to this
src="{$img_dir}{substr($info.file_name, 0, -4)}.png"
first you change the folder where to look for images, from "yourtheme/modules/blockreinsurance/img" to "yourtheme/img"
then use substract function to cut the last 4 characters which are ".jpg" and then after you close the brackets simply add your file type, like ".png"
hope it helps