typedef vector<pair<__int64,string> > viListImage;
typedef pair<__int64,string> piListimage;// размер и имя
....
bool ptr_less_size(const piListimage& lhs, const piListimage& rhs)
{
	return lhs.first < rhs.first;
}
bool ptr_less_name(const piListimage& lhs, const piListimage& rhs)
{
	return rhs.second.compare(lhs.second)+1; //compare возращает -1 0 1
}

....
sort(viLstImg->begin(),viLstImg->end(),&ptr_less_size);
....
		sort(viLstImg->begin(),viLstImg->end(),&ptr_less_name);