Generally speaking, examiners will expect you to have mastered the statistical and econometric techniques from your exam papers. In some universities, dissertations from students sitting joint honours papers are noted as such, so the examiner doesn’t expect the same level of econometric nous as they would from a specialist economist.
Some of the very best dissertations use techniques which go beyond the syllabus. If done correctly, this can be very impressive and will probably be highly rewarded. But it is often better to stick to what you have been taught than to try something that you are not confident doing. It is the nature of econometrics that mistakes are penalised far more than flashy analysis is rewarded.