Can brainwaves from EEG be used to measure enjoyment of media?
I think the question whether this experiment will give you useful data can be split into two parts:


Does the EEG reflect the emotional state ?
Does the stimulus (media,pictures) induce such an emotional state ?


For the first question there is a lot of research going on and this review might be a good starting point to get into the topic. Without knowing much of the literature I would guess though, that you always need some ground-truth data of the emotional state to train your classifier. This would mean that you would need to somehow 'measure' your emotional state during the EEG recording. You could avoid this by separately 'measuring' your emotional state when watching the media but then you would have to assume that it's always the same emotional state which might not be true.

If you don't want to measure the emotional state, you could also try to do unsupervised learning on the EEG signal, maybe saying that you want to find 3 different emotional states and in the best case the algorithm will give you a nice partition of your stimuli into three categories but there is no way that it can know what emotions those categories stand for.

For the second question I guess it would make sense start with a set of stimuli for which you are sure that they induce strong emotions.

All of this is speaking of general emotional states. Reducing the problem to only distinguishing enjoyment vs. no enjoyment would make it a bit easier of course but the aspects to consider remain the same.