I don't think there is any penalty for calling your links page links. After all, Google has nothing against links or even link exchanges. The only think Google is trying to do is to penalize link farms, link spam and any other activity it finds unnormal. There is definitely nothing wrong with having a links page :P
Regarding the number of links I think 20 and even more is fine. If you read
Google's Webmaster Guidelines you will find that you just should keep it under 100. My belief is that it doesn't hurt you if you put a lot of links on one page, but the sites you are linking to will have less of your PR passed to them.
And now something about linking for SEO purposes and PR. People usually look for high PR sites to put their links on. But they don't realize that only the mainpage has e.g. PR5, while the link.html page may have only PR1 and link2.html as little as zero! So I'm never too happy if someone says my link will be on link4 page. But PR is not that important if your link is only on one page as is the case with link pages. What is really great for you is when your link is visible at every page of a website. It gives just so much more power! Example: look at the links at the bottom of my site -
www.poker24.pl - they are visible at every single page of my portal - and Google has got more than 100 pages in its index -
site:www.poker24.pl. Of course it doesn't mean that such link is 100 times more powerful, but it is definitely much much more powerful.
just my 2 cents B)