Very interesting concept, although I find the choice of keys to (subtly) accent to be quite unusual. We'll all OF COURSE have differing opinions on this, but if Caps Lock and Tab are accented, then an accented ISO Enter key would be practically screaming to be added. I think, similarly to PvtSkittles, that accenting F5 to F8 would also be visually interesting. Again: IMHO, YMMV, WDIKAA.
I do have one observation that is not strictly subjective, though: for full US ISO(/ANSISO/ISANSI) support, an R4 \| keycap should be added (or, if necessary, have the R4 <>| key replaced with it... but hopefully both can stay).