It's always very interesting to see these. I do somewhat agree with teioh though, you should be able to have a lot more to share once the anime's over and done, and maybe even when they start selling Blu-rays/DVDs. More information means more interesting.
Though I have absolutely no idea where you can get the figures, statistics and whatnot, I'm sure if you do Japan-only, it'll be a lot easier since they tend to have a lot of numbers for these things. You can also include randomly interesting figures by gathering data from within the manga, if you can think of something more interesting than "number of pages Mikasa appears in" lol :P
In the designing aspect, the main idea is to get information across without having to 'read properly.' This means when you see a graph, you shouldn't have to read every word to straightaway know what the graph is about. This also means the formatting really counts, for example as you can see, in the "manga-cover appearance" section, the more appearance a character gets, the bigger their icon.
A graphic designer friend did slightly similar stuff in quite a creative way some years back:
http://www.visualnews.com/2011/05/18/if-the-world-were-a-village-of-100-people/
The way these are presented is so that you have a general idea straightaway what the chart is about. The massive word in bold font as the title for each graph is very helpful even if you don't read everything.
I think what the One Piece one is missing right now is the lack of funky designs, to give it all a One Piece feel. It could be as simple as using a skull instead of a dot for a point on a graph.
The "manga-cover appearance" is nice, but it doesn't stand out as much as it should. If it were me, I would have made a silhouette of each character and make some sort bar chart using them or something else. Because circles on their own are boring, frankly.
Also, if you look at the 'Popularity' section (last section,) the colours aren't very consistent. The 41% is represented by a dark colour in the first pie chart, but then the next two numbers are represented by a light colour. It's very confusing if you're not reading it carefully, meaning it's not at the full potential of what an infographic can give you.
Negative comments aside, the overall use of colours and shadings are very very pleasant. It makes people think, wow this is pro stuff.
Finally, as good statisticians should do, include your sources and the "All data is accurate as of DATE" disclaimer. If you find numbers from Wikipedia, source their source (located right at the bottom) not the Wiki page itself! The stats-unrelated opening sentence on the One Piece one saying "via Wikipedia" is fine.
Probably more ideas later. I'll stop writing here for now.
