I think you're pretty much there. An hourly rate is a good place to start, and iirc it's pretty much how the industry works outside of the furry community. You don't have to have set prices; I've seen artists have an hourly rate and negotiate it with the client on a case-by-case basis. I personally think that's how all artists should do it, however we're all poor and would like assurances :P So a sheet with some set prices is a good compromise.

Just start with your hourly rate and then make your sheet based on the average amount of time it will take you to finish a project. For example, if a full body sketch usually takes you less than an hour, you'd put that as $25 (always round up, that's expected). If a full piece with all the bells as whistles usually takes you between 3-4 hours, then set that as $100. If you round up, that means you can go over a little and you'd still get paid your fair share.

You need to put a caveat on the sheet that additional charges may apply depending on complexity, meaning that if a client gives you a piece that's way outside the parameters of the sheet then you'd fall back to negotiating at your hourly rate. If you negotiate something with a client and it takes you longer than you expected, usually take that as experience and adjust your prices. If it's because the client keeps asking you for changes, you need to start charging them extra.

I'd say make a list of project types you'd be interested in (eg sketch/ink/colour/shade), work out the average that will take you, round it up to the nearest hour and times that by your hourly rate. Then add some extras on there, like additional characters or stages.

Full body drawing in less than an hour?! UGG, i'm hopeless >///<

No I'm just kidding, this blurb is immensely helpful, thank you!
I'm certainly not opposed to the hourly rate being the "fall back" if something "simple" is actually more work than it seems, etc.

thx again!

Hourly rates are great! I think the hangup is just consistency, people like to know the range that they'll be paying for so they can budget for it. My suggestion is timing yourself and finding the maximum amount of time a specific commission will take you to do and then advertising a price range based on that ratio for people who need to know.

Yeah you're right, that does seem to be the case! I just find it incredibly crushing if you take on a deceptively tricky project and 5 hours in you're like "dammit I'm only getting $70 for this because thats what I advertised and that's what they paid for!" ><; Truly the worst.
Thank you for your input!

Yeah you should cover your back in situations like by having a plan B in mind incase the complexity ends up being bad, my suggestion is to always offer in the high range of time/paid and if it ends up being simple you can just send back excess or change price info before sending invoices.