Modify CCGreeShareDialog::setParam.
 Users can pass CCImage with GD_SHARE_DIALOG_PARAM_KEY_IMG
e.g.)
	// Capture ScreenShot as CCImage
    CCRenderTexture * tex = CCRenderTexture::renderTextureWithWidthAndHeight(size.width, size.height);    tex->setPosition(ccp(size.width/2, size.height/2));
    tex->begin();
    this->visit();
    tex->end();
    CCImage *img = tex->newCCImage();

	// Create CCGreeShareDialog and pass ScreenShot
	CCGreeShareDialog *dialog = CCGreeShareDialog::create();
	CCDictionary *dict = CCDictionary::create();
	dict->setObject(img, GD_SHARE_DIALOG_PARAM_KEY_IMG);
	dialog->setParams(dict);

	// Show ShareDialog
	dialog->show();