A linear gradient.
First you need to specify what direction the gradient is going by providing an angle in radians. 0 is up and pi is down.
The colors will be evenly spaced.
A centered background image that keeps it's natural propostions, but scales to fit the space.
Scale the image to fit the size of the element while maintaining proportions and cropping the overflow.
Tile an image in the x and y axes.
Tile an image in the x axis.
Tile an image in the y axis.