Question about Star Guardian Wallpapers

What are the differences between last years's wallpapers and this year's wallpapers for burning bright champions? The reason I ask is I downloaded all the wallpapers from the client (i.e. the web browser the links opened) and on a whim compared the sha1 checksums of last years' skins with what was available last year and this year. Turns out the sums were different.

Upon further investigation I realized that all the wallpapers this year are around have the byte count of the wallpapers from last year.

For example, Jinx@1920x1080 is 677403 bytes (661 KiB) this year while the same wallpaper last year was 1188943 bytes (1161.1 KiB).

Thanks!