I've put the all together in one image, also with current echo images and some upstream selection – gnome-icon-theme, Tango!, the upcoming Mango! and Oxygen. You can see for yourself (click on the image to get the original resolution):
There's one notable point – all the upstream icon themes use very similar projection types, and we should probably reflect that in Echo as well to better work with them.
Now let's take a look at the Echo sketches. You can see there three parallel projections and three perspective projections. For now we skip the fact that in some angles the package look better than in others and that it would be better if I closed it more in some of them – I decided to make all of the packages exactly same in the original "3D image".
First compare the looks. For me the winner for this section is the second perspective (from the left) followed by dimetric projection. The left-most one would probably look much better if more closed, like in Mango!
Second take a look at usability. Basically all the icons have very good defined metaphor, only the left-most one feels a little awkward in this case - but as I said previously, it would get much better if as much closed as in Mango! So in this category there is no clear winner.
Next we ought to take a look at "desktop integration". All current desktop are 2D and it will most likely stay that for a considerable future that way. So if we go to much overboard with 3D it might get a bit akward. Imagine you are clicking an icon that does not face forward to you, but is is slightly rotated. I feel that that is the main problem in current Echo. That leaves possible good candidets the left-most and right-most perspective icons and cabinet projection, and with one eye closed the dimetric projection.
Finally lets compare them with current upstream. Obviously there is no other choice than the left-most perspective.
During my "trip" to the projection area it appeared that Echo would probably be better off if we
- Reduced the used projections to 2 types (one of which is Flat)
- Start working with perspective projection, with similar setting that is used for upstream icons
- Aim to be 100% consistent with the projection usage
What do you think?