Are you satisfied with the standard cubic design of most cases?

Yup.

What kind of design would you like to see in a guitar case? (retro case design, basic black body with fur lining and so on.)

For shape I would personally like a nice trim rectangle with compartments under the lid (with lids) so when you opened it up you could get stuff out without moving the guitar if you didn't have to.

I think cases should be easily customized. I would want to be able to cover a case with colorful fur on the outside (except for the edges and corners, wouldn't last there) and porn on the inside, but that's just me.

Should the case contain anything else such as a guitar tool kit or spare string packs?

It should have space for those things, but they don't need to be shipped with it. It would be awesome if those were shipped with it, especially the tool kit or something like cleaning/polishing supplies, but I don't think that's the most important issue.

Is the shape of the guitar case a big issue? Would you rather see a case with a unique design but still fulfill its need or would you prefer the usual cubic design?

Cubic, in my opinion. For the differences in guitar shape the padded part for the guitar (the bottom of the case, top for compartments) should be able to be modified to fit different guitars. I can't remember what it's called, those things you can rearrange and affix to do that. It's possible. They're like blocks/triangles you set in place.(?)

Is there anything specific you are looking for in a guitar case? (add anything you want in the case here.)

Nothing I haven't mentioned already, except that light is good. Light is very very good. Also, it's a good idea to reinforce the edges and corners, especially if it's made for travelling. And as long as I'm describing a probably impossible case, insulation is a must. The case should be able to block outside temperatures decently, because nobody like tuning after every time they take their guitar outside.