I already looked at the shader for general_industrial/ironbar and it has "cull none" and "nopicmip". Adding "nomipmap" may be worth a try, but making a new texture shader means replacing all of those textures in the map with the new one. Below is from the shader bible (
http://www.qeradiant.com/manual/ ).
3.2 cull <side>
Every surface of a polygon has two sides, a front and a back. Typically, we only see the front or "out" side. For example, a solid block you only show the front side. In many applications we see both. For example, in water, you can see both front and a back. The same is true for things like grates and screens.
To "cull" means to remove. The value parameter determines the type of face culling to apply. The default value is cull front if this keyword is not specified. However for items that should be inverted then the value back should be used. To disable culling, the value disable or none should be used. Only one cull instruction can be set for the shader.
3.5 nopicmip
This causes the texture to ignore user-set values for the r_picmip cvar command. The image will always be high resolution. Example: Used to keep images and text in the heads up display from blurring when user optimizes the game graphics.
3.6 nomipmap
This implies nopicmip, but also prevents the generation of any lower resolution mipmaps for use by the 3d card. This will cause the texture to alias when it gets smaller, but there are some cases where you would rather have this than a blurry image. Sometimes thin slivers of triangles force things to very low mipmap levels, which leave a few constant pixels on otherwise scrolling special effects.
3.7 polygonOffset
Surfaces rendered with the polygonOffset keyword are rendered slightly off the polygon's surface. This is typically used for wall markings and "decals." The distance between the offset and the polygon is fixed. It is not a variable in QuakeIII Arena.