I think what sometimes causes confusion with OpenGL is difference to perspective and ortho coordinates. Perspective is the default way to render, with positive side going up and ortho positive is to down side.

I don't know if you use perspective but same draw function is usually not good for both. It is possible to play around with:
glScale(1,-1,1) // You can flip the coordinate system around if you want
glRotate(180,1,0,0)
glCullFace // You can rotate the image 180 around X axis and draw only the back face
glDisable(GL_CULL_FACE) // Or you can use this to simply draw both sides
(and enable back when needed for example 3D models)