How to Get a Thumbnail URL
Best image hosting services to get a direct image link for your post cover
Use FastPic.org (Recommended)
FastPic is a fast, free image hosting service. Go to fastpic.org, upload your image, and copy the "Direct Link" (ends in .jpg/.png).
https://fastpic.org
Use ImgBB
ImgBB is another popular option. Upload your image at imgbb.com and copy the "Direct Link" from the upload result page.
https://imgbb.com
Use Blogger / Blogspot
If you have a Blogger account: create a new post, insert the image, save as draft, then right-click the image in the post → "Open image in new tab" to get the direct URL.
Use Postimages
Go to postimages.org, upload your image without signing up, and copy the "Direct link" from the result.
https://postimages.org
Verify the URL Works
Paste the URL into the Thumbnail field in the post editor. A small preview will appear immediately below if the link is valid.
Recommended Image Size
For best results, use a portrait image with a 2:3 ratio (e.g. 400×600 pixels) or a 16:9 landscape for non-movie content. JPEG format at high quality is preferred.