The horizontal and vertical distance between the ellipses can be controlled by the border Width and Height attributes. If you increase one of the two values but leave the other untouched, you can change the aspect ratio of the ellipses. (Image 3)

The Amplify value controls the ellipses' gradient from the center to their edges. Set it to 0 to remove the gradient entirely.

Set the number of rows and columns with the Tiling values.

Use the Displace parameter to control the horizontal shifting of each row in relation to its preceding row.

Transformation of the function result can be very useful for special textures here. E.g. in Image 2 the Bounce transformation type was used to create the concentric rings.