At NSE Imports we like many others use Google Shopping/Merchant/Ads to get our products promoted in various places around the net. However sometimes you get the annoying and slightly cryptic 'Image too small' error appear.
Like us. you will likely search around and find lots of blogs and sites who will all tell you to make sure your image matches Google Requirements. What none of them tell you is that EVERY image for your linked product must meet the requirements.
For example we use the most excellent App for Google Shopping Feed on our store, when you get the 'Image too small' error you look in your product and it will show you this:
So now you're thinking 'Ahhh, that image is too small' and you'd be right for thinking that, but also wrong, that image above is 800x800 so it's perfectly fine, the big green tick says so, you instead begin to question the app, your sanity and more...
Until today I could not figure out what it was, suggestions are made online that maybe the content of the picture is 'too small' for example of there is too large a background to product ration etc..., so pictures get cropped and reuploaded, still no good.
Today, I found the answer and it might help you, there was never anything wrong with that image above, not a thing, it's perfectly fine. However, this size chart image I had temporarily used for this product page....
Is about 700x180 and that's what's upsetting Google, how did I know this? I happened to be looking around Google Merchant while working on some other things and decided to see what it said there, a few clicks later and heading to:
Products > Diagnostics > Image Too Small > View Examples
And we get a nice list of products that are flagged for their image sizes, next to each issue is a handy 'Open Image' link, guess which picture appeared for this listing?
After all that time I had wasted trying to correct the main image because everywhere basically says 'make sure your linked product image is big enough' it turns out that Google looks at ALL your products images through your supplied link and then complains if one of them is duff.
Now I know what the issue is I can can quickly fix it, I'll make a proper sizing guide image at around 800x800 or larger and replace the duff one, on the next scan Google will give this product a clean bill of health.
Hopefully this will help others out there with similar issues.
TL;DR version:
Google checks every image on your linked product page, make sure EVERY image is above the minimum required for your category, or just aim for 800x800 and above and you'll likely be fine.