You have two (sensical) solutions:
- Select "Unicode", then replace every std::string, LPCSTR, LPSTR etc.. in your project with the unicode-counterpart (std::wstring, LPCWSTR, LPWSTR). Also, you need to write an "L" before every string (e.g.: L"C:/Pictures/Test.png"). This should fix your errors, if not, some of your other included libaries might be using multibyte, I'd get to that if his prooves to be the case.
- Keep your project at Multibyte setting, and replace every std::wstring, LPCWSTR, LPWSTR in your project with the multibyte-counterpart (I've already named those).