Iconography is an important part of game design, and I wanted to make a brief pitch to game designers to dabble in graphic design. While you engage with your game abstractly, most players will first encounter your game visually. You are the best judge of whether players are understanding your vision, and consequently, I think it’s important for game designers to understand something of the visual design. I don’t think it’s important for you to make things look really pretty, but it is important to be able to test ideas. Should this icon be at the top or the bottom? Should there be icons for this idea or should it be written out as text? I think these are the types of questions you should be asking. Then, when you likely work with an artist/graphic designer, you can “speak their language” more effectively, be able to show them prototypes and sketches.
For me, it was important to find a tool that was a good balance of easy to use and powerful. I found Omnigraffle to be that tool for me. It’s Mac OS only, and it’s mainly designed for making flowcharts, but I’ve found it to be a great tool for me to interact with my graphic design. I can make quick little icons, layout cards, and so forth. It has no “data merge” capability, the ability to generate a pile of cards from a spreadsheet, but that’s it’s main weakness. I use InDesign for data merge, but find it difficult to use for other stuff. Eventually I may move to InDesign, but I find Omnigraffle is just so quick and easy. I’ve heard great things about Sketch and I imagine PowerPoint might be a good alternative too.