Questions, questions...

Ahh, that brief respite to playing my beloved TDs on bnet was nice, back to the old drawing board again...

Question: I suck &%$# at messing with hero abilities, how can I change the target ability art. This means from something like the Frost Armor art to the Big Bad Voodoo target art.

Question: I'm trying to make a cloud elemental. Is it possible for the unit to look like a little cloud? If so, what is the art file? I can't find it n e where.

Question: What (or where) are the art files for the passive icons. They have to be somewhere. I'm talking about how, when you hit the menu (F10) the abilities fade and become unselectable (like an aura or passive ability). If some1 can find the strings to these art files, you would be able to use any icon you wished to create an aura or passive ability.

Question: What are the special effect (event trigger) strings? the default is "overhead" but there have to be others...

NO MORE QUESTIONS!(Chinese Accent)

If n e 1 knows where this stuff is and/or how to do it, I would greatly appreciate it.

The buff art for spells (the art which is played on units that are affected) is something that we can't edit using TFT's spell editor. You can alter the buffs in the <race>AbilityFunc.txt files and add them to your map with the Import Editor. Instructions for doing that are under the Tutorials tab or floating around here. Do a search (it's at the bottom of the forum screen).

It is possible for a unit to look like a cloud. But, I'm not aware of a model that looks like a cloud that you could use.

When you refer to passive icons, you actually mean Disabled. They are different from the passive icons slightly in appearance, and substantially in usability.
Whenever an icon is set in the World Editor, it automatically sets the Disabled icon to be ReplaceableTextures\CommandButtonsDisabled\DISBTNbuttonname.blp but I don't recommend that you set DISBTN's as passive buttons. The reason for this is that, if your DISbutton ability were disabled, it wouldn't have another icon to look for.
Icon editing and making is not challenging if you have access to somewhat good image editing software and tools like the War 3 Editor or Image Extractor II.

As for your last question, I am morally obligated not to answer. This question appears several times weekly, and the answer to it is peppered throughout previous posts. Please use the Search feature at the bottom of the Forums page. It's worthwhile.