I forgot to update the OpenWrt README... For 3.6, you'll need to change "testing" to "latest"

We now have 3 stages: stable, testing, and latest.

Stable (currently 3.0.x) is "no outstanding regressions from previous release, and probably any bugs found will also affect previous versions too".
Testing (currently 3.5.x) is "only applying bugfixes to make this the next stable"
Latest (currently 3.6.x) is "new code in the works; lolmaybeithascrashing"

That said, 3.5.2 should have had the bigpic fixes too... :/

Did you opkg update?