Pegged with US dollars is still the most common choice for most. Euro and even CNY, I've seen that there were attempts but they didn't became as good as with USD pegged. And we don't need more of them because the USD standard has got a lot of market share already and that's why many of us relies on it. USDT has got $155B in market cap and that's only just one, let alone the others like GUSD and USDC.