I have been spending a lot of time with Centred once of the most difficult things to deal with were the transition areas between similar tile types. Such as grass and forest for example, its hard to see. What would be helpful is using the information in the art.mul for texture date. The image of the title is larger and square. Having this image appear on a mouse over highlight of tile information could be very helpful to see how the transition lines up.
If a "tooltips on/off" option is added than OK - When I work on my laptop I see all clearly and additional popups would only hinder my view.
Nice idea, although popups of any kind are a bit hard to implement on linux, the main platform I'm currently on. So it will probably have to wait until I find a way to do it properly for platform independance.