Anyway to Customise Proxy Error Pages?

As the topic suggest, can I customise the Proxy error pages, such as the

Mikrotik HttpProxy
Error: 504 Gateway Timeout

pages?

not yet, the new proxy is still in development, we may add this feature

ok thankyou for that, it would really be advantageuos for us, so we can provide better information, and put our logo etc on the page.