You cannot overwrite the default files. For particle effects or gui textures, you should replace them via an add-on. For brick textures you will have to wait for this feature to be implemented officially.
Quote from: Jorgur on October 09, 2011, 04:00:14 PMThere is a rumor going around that you can prevent files being replaced by setting them to read-only. Apparently Badspot doesn't like this and silently deletes topics that mention it. Maybe if you pack the add-on to a zip-file and set it to read only you could stop the file downloading and prevent all this silliness?If you do that, you WILL forget up the game. What's going to happen is I'm going to have to make an update to one of the default add-ons and it's not going to work and everyone is going to blame me when it is really 100% your dumbass fault. All I want to be able to do is update my own goddamn loving addons and friends like you ruin it all because you can't be bothered to learn how to program stuff properly. Go ahead and do it but don't be surprised when future versions of the game tell you to forget off because your files are read-only.
There is a rumor going around that you can prevent files being replaced by setting them to read-only. Apparently Badspot doesn't like this and silently deletes topics that mention it. Maybe if you pack the add-on to a zip-file and set it to read only you could stop the file downloading and prevent all this silliness?