So the icons are all from a pack that someone uploaded to the Factorio subreddit a while back called "Unused Renders". I'm basically just using the pack right now as convenient placeholder visuals for the mod while I'm early on in development. Right now, the mod is still pretty open ended and I'm sort of messing around with ideas that seem like they could provide interesting logistics problems. For example, right now (and I believe this is in the version uploaded at the moment) I have a new fluid for "Potent mana" that you make fairly early on. The idea I'm playing with here is that any recipe that uses Potent mana will have a 1:1 byproduct of Spent mana. This, later down the line, will be able to be used for other things such as reprocessing it into Potent mana or maybe even creating different types of mana. I've also been playing around with the idea of having a couple different recipes for certain items. The first example of this is the 2 different recipes for Mana steel in the mod right now — Brute force enchanting and Liquid mana enchanting. The idea here is pretty simple; Brute force enchanting is slow and less resource efficient but you get it earlier and it's an easy recipe. Liquid mana enchanting, on the other hand is a bit faster and more resource efficient, but it has that Spent mana byproduct.
In terms of end goals, right now I'm not quite certain what it'll be yet. I have this vague idea of creating a portal to a specific dimension, because I do want part of the progression being visiting specific dimensions with unique resources and logistics problems (and possibly threats) but I'm still looking into what it takes to add that to the mod. I do also think I'd be remiss not to add new weapons, armor, and equipment to the game, so expect to see that, though probably further down the line.
All in all, I'm still very early on in development here, so I'd love to hear suggestions anyone has to offer!