AVA_BACK - PrincessMtH/sonic-adventure-textures GitHub Wiki

This background, also used in part for the game's title screen, boxart and marketing, is made up of at least four different images. Two of them depict water, each at different distances. The other two depict clouds, one lit from behind and one lit from below.

The backlit clouds are SKY01001 from MIXA IMAGE LIBRARY Vol.15　雲･空天才 (Poetic Impression on the Sky and Clouds). The image is mirrored and stretched, then overlaid over the other cloud image with a blending mode such as Lighten or Screen.

The clouds at dawn are SKY01041 from MIXA IMAGE LIBRARY Vol.15　雲･空天才 (Poetic Impression on the Sky and Clouds). The image is mirrored, stretched, and colour corrected.

The 7th texture in バックの鬼 寂2 (Back no Oni SABI2)'s WATER set. It is overlaid on the top right of the background.

As of yet, no other source images have been identified.