Tang standard of beauty can be seen in Tang era murals and paintings such as this and this this. You can see that upper class Tang women were quite pale and possessed well-rounded figures, as dark skin usually signified peasant status. In fact, in most paintings of Yang Guifei, such as this 16th century one here, slight NSFW, shows that she was rather well-rounded. This lead to the Chinese proverb "Huan Fei Yan Shou" (literally "Huan is fat while Yan is skinny"). Huan is in reference to Yang Guifei's personal name Yang Yuhuan, while Yan is Zhao Feiyan, another beauty who was the wife of Emperor Cheng of Han. The proverb had its origins in a poem by the famed Song statesman and inventor Su Shi.

Upper class Tang women routinely consumed medicine which were said to be good for their skin, applied cosmetic powder to their face, and used lip gloss. They also drew "beauty marks" such as crescent moon, birds, flowers, leaves to their forehead, chin, and cheeks. They also plucked out their eyebrows and drew new ones, a style which was also very popular among aristocratic women in Japan. For more on the appearance of Tang women, I suggest you check out Charles D. Benn's China's Golden Age: Everyday Life in the Tang Dynasty.

As for whether or not a Tang women would be considered attractive today, well that would depend a whole lot on one's personal preferences. If you find plucked eyebrows and well-rounded women to be attractive, then a Tang girl would be perfect for you. But given modern society's preference for skinny women, I would venture to say that Tang women would not be considered too attractive today.