When you hover over an image in the search page with your cursor it gives you some details but not how big the file is unlike sites such as rule34paheal.
Adding this feature would be useful for people using limited data plans trying to only look at smaller sized images and animations.

pro tip: turn on reduced samples which will make all images smaller (in size and file size)

siikaprinssi said:
pro tip: turn on reduced samples which will make all images smaller (in size and file size)

This. With this all images will be 800x800 restricted JPG files which then will be maximum of couple hundred kilobytes. Something like post #1301947 is 61 MB, but with reduced samples enabled it's then it's 57 KB.

Reduced samples are standard with all other boorus and it was switched to be standard here as well not too long ago, however users registered before the change will keep the earlier default as that's user setting for them and it would've changed the setting for everyone who didn't want the change.
Image resize mode

You should also consider blacklisting animated tag as none of the animated formats right now support samples in any way and missing_sample so you won't run into posts that are 60 MB because something broke and there's no sample.