Artist Tips

Light Source

When drawing background tiles, always make sure the light source is coming from the same direction (usually top left or top right). Also, map with correct shadow tiles for extra depth. Don't mix light sources. Shading from outside dark to centre light can sometimes work, but mostly doesn't look as effective. With sprites, flipping will mean this is less relevant, but depending on the game, choose the light source based on the most common facing.

Background Contrast

Try to make sure that your backgrounds are darker or of a lower contrast than collidable object such as walls or moving sprites. This makes them easier to see and help the player unconsciously read the screen more effectively.

Bullets

If bullets are prominent in your game, make sure they are clearly visible. Use high contrast color, animation or even flashing colors if against more complex backgrounds.

Sprites and Animation

The most important thing when drawing sprites is making sure you start out with a good, solid template. Don't begin by drawing a fully shaded sprite, hoping to cover up iffy proportions. Draw your initial sprite in monochrome (or several flat colours) and make sure that you're completely happy with the look of it before continuing. Animating using a flat colored sprite will show you what works, and save a great deal of time if adjustments are to be made.

Perspective

Try to keep perspective consistent, especially in overhead style games. Foreshortening often does not work and can look unnatural(i.e, Red Alert)

Texture

Varying the style of shading can significantly alter the perceived texture of an object. A lot of dithering can make things look rougher, older or dirtier. See the examples below, both of rock, but using very different shading styles.