IEEE full article with small images or more than 8 pages
In many, but not all IEEE publications, the hard limit implies that if the paper is larger than N pages, every (N+1)th page is charged with an overlength charge. See this page on IEEE Author Center, which also contains the fresh link to a PDF with current prices (overlength, open-access, color).

Usually, IEEE Transactions on XXX will allow publishing papers that are larger than standard size (up to a certain maximum), while the IEEE XXX Letters-type journals might have a hard limit with no possibility to publish a paper exceeding the standard length even for an extra fee.

I would certainly check the journal (not the general IEEE guideline) you are intending to submit on that matter since you want the images to be legible without a mandatory zoom. The fees vary, but, for example, IEEE Transactions on Antennas and Propagation (TAP) charges $200 per extra page (as of 2020). See this 2018 guideline for IEEE TAP which covers more details on how references count and fees are calculated.