Can you boost quality of app?

I was wondering if you can "boost" the qaulity of an app in app inventor....

My app looks pretty pixelated, and low quality, but maybe it's because I just recently checked it out with a tablet. Does is have better qaulity on a phone?

Also, the little bar at the top of the screen, looks REALLY unprofessional, and has very low qaulity... Is there any way to remove it, or boost it's qaulity?

One last question. can you make your icon multiple sizes, so it i suitable for most screens (hdpi, xdpi etc.) ?

ANY HELP PROVIDED WOULD BE GREATLY APPRECIATED!

ad 1: App Inventor and the Screen Size

ad 2: use App ToMarket to remove the title bar

ad 3: see here Solution for tablets on Google Play by J Martin

Advice: Before posting, it's a good idea to search in this forum. Many others have likely run into problems similar to yours. How to search see screenshot.

See also the  Top 5 Tips: How to learn  App Inventor