How to extend the Costume Changer
First off lets start by saying you need to understand what files are attached to what files. You also have to be comfortable with using explorer and some sort of image editor and possibly some sort of screenshot program.
This is also somewhat hit and miss and rather advanced. Sometimes this trick will simply not work correctly
1) Go download a custom costume. I'll be using the
Makoto Half Kimano for this example. Make sure you take note of what costume it's based on. In this case it's costume 1
2) Go into the correct folder in super street fighter IV for that costume. Copy all the costume files for the noted costume in step 1 into a new folder. For this example it's Makoto's first costume, so i copied all MKT_01 files to a new folder
3) Extract the custom costume into that same folder you just created. If prompted overwrite any files.
4) Now the tricky part. You have to fix the names. The costume number has to be the next available slot. Going by the example Makoto has 3 costumes built in, so this would be costume 4. So rename all the MKT_01*.* files to MKT_04*.*
5) Take all the files you renamed and copy them back into the regular character folder. In this case it's Super Street Fighter IV\resource\battle\chara\MKT
6) Now go into the Super Street Fighter IV folder. There's a sub folder name Images. Go to that folder. Inside the folder are images based on the folder name and costume number. In this case it's MKT01 through MKT04.jpg
7)There has to be an image for each custom costume or else the program will start throwing errors. The image name has to follow the same number as the files you renumbered. In this case it's MKT04.jpg. Copy one of the other image and rename it to the correct name. In my example I took MKT01.jpg, made a copy and renamed the copy MKT04.jpg
8) Fire up the costume changer. If it all worked right there should now be a 4th costume option for makoto. Select the 4th costume and run the game
9) To get the right picture you'll need to take a screenshot. Run the game and go into training mode. Select the character you just added and the correct color (in most cases it's 1). Select anyone for the other player and go into training mode
Now take a screenshot. You could use steam to do it, or with vista/win7 you could hit alt-enter to run it in a window and hit printscreen.
Now open your image editor. Either load the screenshot or paste it into a new image. Crop whatever half of the picture has the custom costume. Then take the remaining picture and resize to 356 x 400. Now save it into the images folder with the same name as you used in step 7