2D Background Resolution

What resolution do you guys make your 2d backgrounds, if the background is static or non moving like cut the rope?

How do you handle or scale this for multiple platforms, here's the platforms I want to first support:

Resolutions:
Surface 1 RT = 1366 x 768, AR = 16 : 9 = 1.78
Surface 2 RT = 1920 x 1080, AR = 16 : 9 = 1.78
Surface Pro 1 = 1920 x 1080, AR = 16 : 9 = 1.78
Surface Pro 2 = 1920 x 1080, AR = 16 : 9 = 1.78
Surface Pro 3 = 2160 x 1440, AR = 3 : 2 = 1.5
iPad3 = 2048 x 1536, AR = 4:3 = 1.33
iPad2 = 1024 x 768, AR = 4:3 = 1.33

Thinking maybe work in the highest resolution and scale back as needed?

Thanks,

Vanz

 

Usually for backgrounds what I do is to keep a single image of res. 1536x2048 and add it on the center of the screen. No scaling is applied on the bg so that it doesn't looks blur. Rest of the game content is scaled as per different resolutions.