The best person to ask about final deliverables is the contest holder. Often, they have specific requirements, which they should have made clear in the brief. If they didn’t, you should ask them in the contest discussion. You must give the contest holder editable files.
For website designs, Twitter backgrounds and other bitmap images
Designers should provide a layered RGB file in Photoshop PSD or Fireworks PNG format. PSDs (Photoshop) are raster-based editable files and are mainly used for web-based designs. It’s a good idea to also provide a flat JPEG version, as this demonstrates how the layered file should appear.
For logo or some other VECTOR image
Designers should provide EPS, AI, PDF, or SVG file format. AI (Adobe Illustrator) is a vector-based file that must be used for logo designs. For vector designs that will also be used for print, providing a CMYK version of the required files is your best bet. If the brief called for one-color pantone, or anything specific, you should also bundle that in. And, just as you would for website designs, you should provide a flat JPEG for the contest holder’s reference.
If you use CSD (CorelDRAW), you should provide the contest holder with an editable PDF or convert your file to AI. For more information on the problems that can occur when doing this, take a look at CorelDRAW Problems: Publishing as AI and EPS.
Any commercial fonts included in your design should be rasterized, outlined, or acquired legally by the contest holder.
Remember: the contest holder may require additional files (TIFF, GIF, etc.) so check with them and give them the files they request.
Learn more about different files formats by checking out File Formats Explained: PDF, PNG and More.