The panorama background (image on the main screen) included in the JAR is the images from the 1.13 version (Update Aquatic). When the external ressource file fail to load, the background image is the ocean instead of an image of the news villages.
The source of the problem is the images in this folder inside the JAR:
\assets\minecraft\textures\gui\title\background*.png
You should include the village background inside the JAR, then remove it from the ressources file.