The documentation stipulates the SAFEARRAY must be an array of VARIANT that contain IDispatch interface pointers, so you could do something like this (I'm using smart pointers which is easier...):

CComPtr<IFileSystemImage2> image;
CComPtr<IBootOptions> options;

image.CoCreateInstance(CLSID_MsftFileSystemImage);
options.CoCreateInstance(CLSID_BootOptions);

// set various options here...
options->put_Manufacturer(CComBSTR(L"joe"));

// create a SAFEARRAY of VARIANT
CComSafeArray<VARIANT> a(1);

// create a VARIANT of type VT_UNKNONW (or VT_DISPATCH)
CComVariant v(options);

// put it in the array
a.SetAt(0, v);

HRESULT hr = pImage->put_BootImageOptionsArray(a.m_psa);