Best Way to Automate Between Excel and PowerPoint?

Firstly, when the target content is in PowerPoint, I would always start writing the code in that VBE. Why? Because you can use IntelliSense to access the PowerPoint OM without having to mess around with library references and/or early/late binding considerations.

Secondly, if you're pasting pictures, you need to be aware of the pros and cons of using raster versus vector formats. If you want to scale beyond 100% and don't want to loose resolution then you need to use a vector format such as EMF or maybe even the new SVG format. That's another reason for coding in the PowerPoint VBE because PasteSpecial behaves differently and you have more "presentation-centric" formats in the PowerPoint library as follows:


Note too that if you go for a raster format, you'll be better off with PNG, usually, because it's a lossless format and PowerPoint has lots of "compression" peculiarities under the hood, more so when dealing with JPG images.

Table correct as of Office 365, PowerPoint 2016, Version 1803, Build 9031.2004

I am a little lost in your solution as I am not sure where/how to code it. Do you have an example or is there an article you could point me to in the right direction.

Thank you