For an mITX board, the bundled goodies are pretty good. A full list of what I found is below:
User's manual
1 x Quick installation guide
1 x Support CD
1 x I/O shield
2 x SATA data cables
1 x CPU heatsink
1 x Watercooling bracket
2 x SMA WiFi antenna cables
1 x WiFi-802.11ac module
1 x ASRock 2.4/5 GHz WiFi antenna
1 x ASRock U3 to U2 adapter
First, you have two adapters here that can help you get the ASRock X99E-ITX/ac installed. The first is a bracket for AIO waterblocks, so you can add in some cooling that will allow for an overclock. The second is a USB 3.0 to USB 2.0 adapter ASRock included should you want use an older mITX case. The plug simply goes between the case's USB 2.0 wiring and the board's USB 3.0 port, which ensures that those USB panels in front work regardless of which case you buy.
Next up are a group of parts for the board's "ac" function. These are optional and don't have to be used, but for those that do, there's a mPCIe card and a supporting bracket, cabling for the antennas, and the antennas themselves. Everything has been bagged up nicely, including the screws used to attach the mPCIe card to the X99E-ITX/ac's surface. However, it might be easy to miss one of these bags, so I've shown them as they arrive to make sure you know what to look for. The provided IEEE 802.11ac card runs at up to 867 Mbps, while also adding in Bluetooth 4.0/3.0. The antennas are equipped for 2 x 2 diversity technology.