Hello there,
The most easiest way I found to take some of the greatest motivational quotes in english is literally by just searching the google for: "motivational quotes " and just navigating directly to the tab where it says "Images".
There you could find literally ton and ton of great motivational quotes possible.
But you could also do this on youtube,
There are millions of channels out there about motivation and most of the time they do motivational videos including so many motivational quotes.
Hope this answers your question,
Best Regards,
Nesim