Excuse my ignorance (I never had the opportunity to use D3D11 since I'm stuck with XP for the time being), but wouldn't there be a D3DX function that loads various texture formats including .png files? I know it's good not to rely on D3DX when possible either way.
However it has been depreciated in windows 8 and therefore the future. Might as well learn the 6 or 7 lines it takes to load image data using FreeImage, and the few more to send it into directx. This allows you future proof and you could switch to openGL as well if you wanted.
Also rolling your own .bmp and/or .tga loader is a piece of cake if you can find the right header info for your image exporter. This will be a great learning experience, and as long as you are just learning and/or using small projects the extra size of the image files won't really matter.