You might be able to use NextDNS to block various third-party servers which are popular for hosting images.
A little fiddly to set up, as you'd need to create a custom block list, and you won't catch all of them, but you should be able to eliminate most of it.
It's nice & light in itself & though it is mostly used to reduce tracking across the internet, it could work well for reducing data generally.
If you are using an Android phone, uBlock Origin as wn extension to Firefox could also be of interest to you (can block images over a size you set, and allows fine-tuned exceptions per site).