You need to make your doors as a model in a modelling program the shape you want them to be.
You only need make one door and apply a texture to it appropriately - then copy it and rotate so it faces the other correctly. Now you have a set of doors.
Now you need to save or convert it somehow into to an .x file model.
You can use a copy of a default FPSC door or set of doors as a starting point. Find and open a default door script and track down all of the necessary associated files and copy them to a new location, rename them so that you can edit them all and leave the originals intact.
Now in the script file you will find references to all files you will need - you can make a x.file new model and textures for it or you may even possibly be able to use your new copies of everything and edit the .xfile model and textures to your likeing - if you are not good at such things - that may be your easiest option. The results however will be variable if you need to make big changes. e.g. the texture wont fit correctly.
If you can make a new model and texture then do so, using the default copies as a guide for size etc, by opening them in your modelling prog and the texture in your paint prog.
Once you have all of your new files made then you put them in the appropriate FPSC locations (look at the script file to see where the should be located if you dont know how to place them elsewhere)
Then having everything in the correct location - in FPSC editor place one of your doors (you need double doors in the pic instance, but if you made just a simgle door)place and rotate your two separate doors appropriately. Or your set of double doors if you made them as a set which you want to use as proper double animated doors.
If you are new to all this it sounds complicated but its not - one step at a time will do it.
FPSC comes supplied with a number of similar Doors and Corridors which would really suit for these kind of situations. By and large you may not need to make anything else complicated but use copies of the default ones and just make your own textures to fit using copies of the default ones as a guide. In the case of the broken doors as shown in the pic - with a little ingenuity you should be able to take a copy of a Default double door set and make it so that you can have it as two separate pieces (just one is needed in fact) that you can place and rotate one independantly of the other as with the broken door pic quite easiy with very little work.
If you want textures of a particular design or quality that have a particular look and feel which adds to the feel of the quality of the environment, then thats down to you to make them if you have the skill or get someone else to make them or buy some professional textures.
Certainly its not difficult to acheive the quality you see in the pic you show - FPSC can acheive that by default - using default textures and models - the final quality of appearance of the environment in FPSC will depend on the skill of the level designer, the textures used, the wise use of lighting, the final choice for in game resolution of the displayed textures and the system and Video Card of the target gameplay machine.
Hope that helps a little.
