Just a couple of problems with some of the battle challengers that are immediately noticeable from the challenge page!

The Rimeflare Hatchling's image is not square, at 226 x 300px; as far as I can tell it's the only one, so it overflows the table on the challenge page. Most of the other challengers are 300 x 300px so fit the table snugly. It's clear to see in the Secret tab as it is misaligned against all other challengers. It's unlocked using the Rimeflare Tablet in the Millionaire Centre.

The other one with a problem is Eclipse. Its image is too small. It's 200 x 200px while everything is scaled down to ~75% on the challenge page, to 223 x 223px. As a result, the image ends up blurry on the challenge page!

Both should be pretty quick fixes as they just need white space added, hopefully! :)