By combining lashes of different lengths and weights, very different effects can be achieved. Here are some typical looks.
Your lash extensions will simply follow the shape of your natural lashes, and increase their length uniformly. (But the extension lashes will taper off at the inner and outer edges, because otherwise they will brush against the bone above the eye socket.)
The choice of eyelash extensions is designed to create a rounder look at the top of your eye by placing the longest lashes in the middle of your eyelids above the irises, and shorter lashes on either side. So, your extended lashes will be longer over the iris and shorter on either side. The effect should be to make your eyes seem more round and open.
Your extensions start with shorter lashes in the inner corners of the eye and then increase in length, step-by-step, right to the outer corner where the longest lashes will be placed, and they will have a dramatic sweep outwards.
A popular variant of the cat eye is the ‘kitten eye’. (Sorry no image.) This is like the cat eye, but instead of lashes increasing in size right to the outer edges, the lashes will taper off sharply at the outer corners of the eyes.
This copies the way eyelashes are always done on childhood dolls, with lots of lash the same length right along the eyelid (except just in the inner corners, where there is a sudden fall to short length).