Bopflop, when we name these things, we try to give the most accurate name possible. For this particular enemy... I'm actually not even convinced there isn't a skull on its back. We hardly get a look at it and barely can see any of the top of its body. All I do see is some color differentiation which perhaps could be a skull. In Zelda Nomenclature the term '-tula' seems to refer to spider like creatures. (Skulltula, Walltula, etc...). Some prefer to use the term skullwalltula for walltulas. If you take a look at Twilight Princess, we had this enemy...
http://www.zeldawiki.org/images/f/f9/Skullwalltula_TP.png
That guy doesn't have a skull on its back at all. In fact, it is just a spider crawling on the wall. To me, 'Walltula' would be the best definition, although Zelda Wiki stuck it in the 'Skullwalltula' section.
I think for Skyward Sword, Skulltula (or perhaps the more plain... 'Spider') both serve as good descriptions for what we know right now.
One thing I'm shocked is that... if somebody was to talk about the inaccuracy or 'fan-names' of some of these creatures, there are plenty of other enemies in Skyward Sword that we just made up the names. Electric Rolobite, Fire Snail, Mechanical Totem Pole, Mechat, and Watchdoor. Either way, as Locke said, most of these enemies will never have 'official' names. The folks at Prima Games might assign them their own 'made up' names, at which because that gets the seal of approval from Nintendo, those become the unofficial names of most of these... at which point in time we'll likely change the names from our enemy guide.