What is the best "last slide" in a thesis presentation? There are some possible options as the last slide of a typical thesis presentation. I've heard of some possibilities:


A question-mark image (as the time to be slaughtered by the referees!),
A Thank You declaration (There are some negative viewpoints about these two options.),
A slide including summary of the presented ideas,
A slide reflecting the presenter's contact info (I think it does not really make sense for a thesis presenter.),
A slide including a quote (I really doubt it's the best way.),
...


What is the best practice to arrange the last slide, then?!
The last slide will typically be seen for some minutes after you finished talking – until you jump to some other slide for addressing a question. This is something that you should use. If you ended your talk with a summary (which is a good thing in most cases), leaving that slide gives the audience opportunity to reflect on your talk, remember what they wanted to ask a question about, or just let your central messages sink in. If they do not want to do this, but focus on the questions, they are not distracted by anything new that you didn’t talk about.

The main exception is if you find it difficult to orally convey that the talk has finished – in that case a thank you slide or an any questions? slide may be the lesser evil and save you from a few seconds of awkward silence that everybody needs to realise your talk is over. Note that you can use such a slide as a backup behind your summary slide – if you manage to finish your talk on the summary slide, the audience never gets to see it. If you botch it, you can quickly jump to the summary slide.

In most situations, however, I consider thank you slides and any questions? slides pointless, as they do not tell the audience anything new and are things that you or the chair have to say. A quote would distract the audience from the questions – unless you are going to read it, but then the quote has to really fit the occasion. Your contact information does not need an entire slide and can usually be fitted on the bottom of the summary slide.

Finally note that on some rare occasions, the following order of slides may work:


main talk with main results
summary and outlook
one or two appetiser slides illustrating first steps into what you just announced as future work, e.g., to show that you paved the way for something interesting.


In this case, you can either jump back to the summary slide or stay on your last appetizer slide – depending on what is more attractive.