We do not prohibit the posting of modified valve maps.
That said, please take the time to read the following before you do so.
Here at TF2Maps.net we strive for unique and original work while trying to maintain a higher standard of quality and ethics. Mappers are here to share in thoughtful discussion and better themselves in their art.
The majority of users on this site do not approve of, respect, or appreciate modifications of Valve maps with the intent of a serious release. There is little value in a map that merely has different lighting or an unthoughtful game mode change. We see Valve maps primarily as a source of education and insight into how various functions work.
If you have edited a Valve map and intend to post it here more likely than not you will be met with criticism unless you have put serious thought into it and made considerable alterations. This does not mean we condone flaming of users who edit valve maps, and cases of such will be removed.