This is what I was going to say. Sometimes it may depend on your audience as well. If you have a board for more mature or older members then too bright can be hard on the eyes.
I joined a few promo boards over the weekend and some of them were near impossible to read.
I gave my members the choice of Dark & Light theme but they overwhelmingly chose the light theme. But there were enough that wanted a dark theme that I decided offer both. They can choose which one they prefer in the user profile or simply going to the Portal and top right where it says Board Style, change it for that session (guest are also able to do that). My light theme is the default since it did win the poll but like I said even guest can change to the dark theme via the portal!
It's twice the work since if I install a mod, I have to do it in both styles. Also I had to be careful of shared color since they display different in a dark background from a light background (such as usernames and ranks).
I'm in the process of changing my dark theme Black Pearl which is a Subsilver2 base theme to Extreme Dark Red a Prosilver base theme. Now both of them are available since I'm still playing around with the EDR theme. But within the next week or so, the Black Pearl will be phased out. This will help that I don't have to no longer do Subsilver edits when I install a mod. My light theme is already a Prosilver base theme.
I like light themes. Light themes makes the forum look more open, which is better in my opinion. Darker themes just make the forum look smaller and more crowded
Dark themes can be attractive. Light themes are more official. Go with a dark and light mix, an example for a forum: Dark Background, light forum section... Black Back ground with a white vanilla forum section.. I say white vanilla because it adds more depth its not just like "oh white" its more of a sleekish color and mixes better because of the depth.