I've got a feed at http://feeds.feedburner.com/core-by-taecho but iTunes won't display the new episode: http://itunes.apple.com/us/podcast/core-by-taecho-group/id534101097
Also art work doesn't show up inside iTunes.
Your latest episode was only published yesterday: it's showing when subscribing, but it usually takes the Store a couple of days to dosplay new entries, so it should turn up fairly shortly.
Your image appears in the Store. Are you talking about when subscribing? That images doesn't appear when subscribing: you have to embed the image in each episode's media file - please see this page:
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