First of all, I checked your website from mobile here, and it loaded instantly ... Also the first image. Perhaps everything loaded within 1-2 seconds. When tested from Pingdom, the website loads at 2.92 seconds, and has a score A 95:
https://tools.pingdom.com/#!/eMjKF/http ... alier.com/
There is nothing wrong with loading on mobile ... You should probably try again. Keep in mind, the FIRST time you view newly uploaded images (from another device), your server will need to resize the images for the first time before storing the image in the X3 image cache. Therefore, images load slower when visiting pages with new images. Also, image-sizes loaded on mobile are different from image-sizes loaded on desktop, and therefore, will need to get processed separately on server when visited first time on mobile.
HOWEVER, I am wondering, if you are doing evaluation, why are you using the very very old X3 0.15? We are currently on
X3 0.22, and specifically
X3 0.18 had a lot of speed improvements. You really should be using a new version of X3, which has improved tremendously since your X3 0.15.