MopiShape (was MopiShape Draw) is a vector drawing app using bezier lines. It is suited for making a relatively small illustration such as icons but not recommended for a large poster. You may enjoy the simple vector-based drawing with it.
Different from paint brush like apps which use pen or brushes to draw lines, MopiShape defines lines using several points such as start point, end point and curve control points, etc. It makes easier for you to adjust lines. You can try until you're satisfied with your work.
When you've completed your work, you may export final image to common image format files. MopiShape can write tiff, png, jpeg, gif and Windows bmp format.