Yes, you can do that exactly as you describe.
I made a 2D game a few years ago where an artist decided to make all our "sprites" as meshes in Blender, due partly to a limitation in the v1.0 of the engine that didn't support textures (the engine I wrote for the shipping version did, but the character art was already made and the meshes were smaller than the corresponding rasterized sprite sheets would have been).
Note that that arrow is a bad example of triangularization. You want to avoid long and thin triangles. Rasterization hardware often works in such a way that works more slowly with long and thin triangles than with shorter triangles. This desire to avoid long triangles applies to many other contexts where triangularization is used, like navmesh generation.