OK, for the slow down, your models may be too high poly, which means they are too high in detail, same thing with your sprites. Cutting the sprite up would actually slow it down, because the engine is rendering more sprites.
To get an image by your name, find an image on the web and RIGHT CLICK on it. First, find dimensions, and make sure they arent too too big (for they will be resized to 50*50) I would make sure its no more than 100*100. Drag down to PROPERTIES and there will be a URL there. HIGHLIGHT the URL and COPY it to your clipboard (CTRL+C) and then go and edit your profile, by clicking PROFILE on the bottom of your page while at the forums. Then click DISPLAY, and go to the text space where it says AVATAR and CLICK in that space. Next, press CTRL+V and your URL should apper in the AVATAR TEXT BOX. Below that box, there is a drag down box labled AVAILABLE AVATARS. Make sure that box reads
-No avatar Selected- Next, click update profile, and BOOM!
Hope that helps
Being polite is ALWAYS a good thing x-d
RPGamer