Nice tutorial! It really explains well how to make Graphics, and not just for SMW, for any game, in a kind of 'retro' style! I know well how to make graphics in this kind of 'retro' style, and I feel i should mention some stuff:
Sometimes while making graphics you need to make some more complex shapes, with more curves, like a bird for example. Compare these two variations of a bird:
The right bird is the same as the left, but with one, crucial difference: instead of making curves that are a rought transition beetween vertical and diagonal lines or diagonal to horizontal lines and vice-versa, the transitions are smooth, look:
In a rough transition, the diagonal line is clearly distinguishable, while in a smooth transition, the vertical line, keeps getting shorter and to the right, progressively getting less like a vertical line and more like a diagonal, and the same way as before, switches to horizontal, progressively transforming, instead doing it all at once.
while making small graphics pixel by pixel, getting the right shape to fit in such small space can be a problem sometimes, look:
No matter how I modify the shape, it doesn't look like part of a circle while still fitting in that small space. The solution is: Use antialiasing, doesn't matter if it's inside or outside, as long as your shape looks good and matches the graphics style you want. It acts like the intermediary beetween "Looks like an octagon" and "Too diagonal" and doesn't make the line look too thick.