Open Photoshop and create a new image, 100x100

Using the eliptical marquee tool create a cirlce that covers most of the canvas and fill with #DDDDDD:

With the circle still selected go to Select » Modify » Contract and set to 1px then press OK

With this gradient:

Drag it from bottom right to top left.

Draw another circle using the eliptical marquee tool around a 1/3 the size of the face and fill this with a white to transparent gradient from top left to bottom right on a new layer. Then Ctrl + Click the face orange gradient layer and go to Select » Modify » Contract and set to 1px then press OK.

Then go to Select » Inverse and press Delete on the white gradient layer.

Now to create the eyes. Using the eliptical marquee tool draw an elongated elipse vertically and fill with white on a new layer.

Use the eliptical tool again with a horizontal elipse and delete the bottom section.

Do the same again but with a vertical elipse on the inside of the eye.

Add a 1px stroke to the eye and just chose one of the colours near the bottom right. I've used #FFC301. You can also add a gradient overlay of #FFFFFF to #EDEDED (or another light grey) with white being at the top of they eye.

Duplicate the eye then go to Edit » Transform » Flip Horizontal and move it to the right position

Either using a small hard brush or the eliptical tool create small black pupils.

Using the same techniques as you used for the eyes do the same with the mouth by using the eliptical tool and deleted the areas you don't need. Alternatively you can use the pen tool, but with small images like this i prefer to use the marquee tools.