I use the iTunes store api to retrieve data from a film. Now I find only the thumbnail to small. The biggest thumbnail in the API is 100px. Is there a way to make it bigger without losing quality?
itunes store api thumbnail
>Is there a way to make it bigger without losing quality?
No - if the image data isn't there, making it bigger will only make it worse.
As well, be sure you're not violating the review guidelines...
4.5 Apple Sites and Services
4.5.1 Apps may use approved Apple RSS feeds such as the iTunes Store RSS feed, but may not scrape any information from Apple sites (e.g. apple.com, the iTunes Store, App Store, iTunes Connect, developer portal, etc.) or create rankings using this information.