General principles:
1. Textures on models have to be with a full set of mips
DXT1 - if there is one-bit alpha or no alpha at all
DXT5 - if there is a complete alpha (windows, other objects with a translucent surfaces)
Examples:
/entity/constrution/entourage/brand_gate_right_t2/walls_bg03.tga: few mip levels (1 of 11)
or
/entity/construction/town_hall/common/2166701526_9b03d6f418.bmp: few mip levels (1 of 9)
Need to resave in the dds format with all mips
/texture/common/construction/bridge_basis#1.dds: few mip levels (3 of 10)
The chain of saved mips is incomplete, need to save once more with a full set of mips
2. Textures of the interface and service sprite objects should be without mips, thus such formats as jpg png tga bmp or dds without mips can be used.
Backgrounds, mini-maps, loading screens, preview images - can be saved in jpg with the maximum quality
Examples:
/entity/service/map_point/tex0_0.dds: extra mip levels (3)
Need to be resaved without mips
/interface/scene/structure/ba64/scheme.tga and portraits of the units - to do nothing
3. Textures with alpha in tga format must always be 32-bit