When I was building SFML for the Nightly Builds, I ran into the following warnings. I think most of the are only related to x64 builds and I'm not sure if we change the stb_image code, but here we go:
SFML\src\SFML\Network\Packet.cpp(408) : warning C4267: 'Initialisierung': possible loss of data 'size_t' to 'sf::Uint32', possible loss of data
SFML\src\SFML\Network\Packet.cpp(437) : warning C4267: 'Initialisierung': possible loss of data 'size_t' to 'sf::Uint32', possible loss of data
SFML\src\SFML/Graphics/stb_image/stb_image.h(760) : warning C4244: 'Initialisierung': possible loss of data '__int64' to 'int', possible loss of data
SFML\src\SFML/Graphics/stb_image/stb_image.h(773) : warning C4244: 'Initialisierung': possible loss of data '__int64' to 'int', possible loss of data
SFML\src\SFML/Graphics/stb_image/stb_image_write.h(321) : warning C4244: 'Initialisierung': possible loss of data '__int64' to 'int', possible loss of data