The reason why Images that are posted on that will only show "Bitcointalk Image Proxy: Invalid Image" is because the image file size limit is 2.5 mb and if the image file size are more than 2.5 mb then expect seeing Bitcointalk Image Proxy: Invalid image in your post. If theymos will increase the file size limit then it would be possible to post images that are more than 2.5 mb without a problem. My solution to an image with more than 2.5 mb in size is to take a screenshot (for mobile phones) and print screen + mspaint (for desktop, save as either .jpeg, .jpg or .png) then you'll see that the file size is low compared to the original and the quality is almost the same as original (it works for me).

Just make sure that the link you are using when posting an image ends with .png, .jpeg or other image format that the forum supported. Image hosting service link does end with image formats like .png, .jpeg or .jpg.

IMAGE FILE SIZE LIMIT