That's odd, the pictures should be working.
Anyway, as stated above you'll want to wear something that buttons up. I'd suggest wearing cotton, also. As sitting in the same spot can cause you to sweat which will bring even more discomfort. They had told me I could walk about my room, but they failed to mention any time I wanted to stand up to even use the restroom or move to a chair I had to call a nurse and have them 'escort' me.
I had mine done mainly because my medications weren't working so they wanted to see how I did with it compared to without it. They also wanted to better pinpoint a location since my EEG's tend to vary in regards to seizure activity location(s).
You should bring conditioner and johnsons first aid cream. I imagine you'll want to rush home, so once they take the electrodes off - put cream on your face and conditioner on your hair. Toss a hat on and rush home - then you can clean up better there.
I'd also suggest bringing a laptop computer, dvd's, books, video games, and/or anything that will keep you busy because it's totally boring. I'd also bring snacks, or set it up for someone to bring you dinner because hospital food stinks.