Maps are .bmp images that can be edited with any image editor. We have a simple in-game map editor for internal use, but we're unsure if it's complete enough in its current condition to be released publicly. Our map designer has been very happy with it though. I'm not very familiar with the map making process, but the data from public sources needs external applications for sure. We're waiting for feedback from map makers in the future, so the process of making maps can be improved. There's an interview with our map designer available here.
2) Unit graphic image
All unit and terrain textures are moddable.
3) Music / sound effect (gun, engine, explosion, shell sound and etc...)
Sounds are more or less moddable.
4) Graphic effect (explosion, flame, smoke, wreck, etc...)
The particle sprite graphics can be modded, but the particle engine is hardcoded.
5) Are there any voice in this game?
Currently there are random casualty screams.
Are there any modding tool and modding tutorial/manual (especially map making) planned to support?
There is an in-game database editor. Other than editing and adding factions, units etc, external tools are needed at the moment. We're listening to the community and will build the modding aspect further based on the feedback.