I am working on a 2D unity mobile game and would like some advice on how to save as much MB's as possible with my background images. I can either create 15 600 x 1000 png images through an image manipulation program and import them into unity, each image is roughly 300 kB's before building the project. Or I can import a base background image that i would use multiple times, and also import a sprite sheet with scenery, and just place the sprites on the background layer of my game scene. Note, if i choose the second option there will be 30 - 100 tree sprites, along with enemy and player game objects in view of the main camera at a time. I'm not sure if this second option will bog down the game, because of all the individual sprites on the screen at once.
Already having gone through the process of making a mobile app, here are my thoughts...
1) If you are looking for a static background, just do the first option and create a image of the entire background.
2)If you are looking for a dynamic background, do the second option you suggested.
In my honest opinion, I would rather draw one image and be done rather than 10-100+ different things which will potentially slow the game.