I might be wrong but they seem to be system caches (and MIUI backups), in addition to your /cache partition the system may need to make hash files and use "Misc" as a virtual temp space; much like windows does in the "c:/Windows/Temp" folder

I am not sure about any of this, its just speculation from looking into my own 3.4GB "Misc" section of MIUI.
Hope some of this helps.

 

Hmmm that is kind of concerning, but it seems it would not be so obvious if it where malicious. But hopefully some one who would know what it is will come along soon! sorry I can not shed light on it.

 

Not sure, but go into recovery clear dalvik cache, that might clear up the MIUI_Theme, and clear cache partition, that might clear up the other files.

 

Looks a lot like themes to me. Are you downloading any? Plus those are on your SD, meaning they were probably downloaded. That's a fact. If they equal up to 1.1GB, and the Triumph has 1GB of ROM, already used for the system, there's no way. Maybe check what's caching to SD or something?

 

its cache and app data, like if you download Modern Combat 3 (like I did) and let it download an addition 900MB of content, that content goes on the SD card.

the problem is the miui file browser doesnt know how to sort files that arent .mp3, .jpg, or .apk and so on, so it lumps the others into "misc"

if you go into the SDcard from a PC, you can check the file size of individual folders and you can see if the cache is the hog or the app data.

for ME, its the app data, i have some huge games installed, for others who dont game, the majority of the used "misc" space could be cache data.

I can see how this would be confusing looking at it from that file browser page, but its not a major problem.


the miui_theme files are the cached images that it downloads when you look in the "online themes" section, it has to download the tiny image previews, and the big previews when you select them. these actually should get cleared, but they will re download if you go back to the theme choose and look at online themes

 

I felt like this rom just changed your options, showed you a little more, those weird files were probably always there. they seemed to be only image cache for me...303 files of it...picsay pro and MMS added it, delete em no biggie. CM7 or stock doesnt have an option or folder called misc. to collect them and show them all together, these are usually a file from here, a file from there, cache ready to be deleted the way i see it.