First and foremost: make sure your Joomla! extension or template is built to integrate with K2. If it doesn't, we won't publish it and this is not the place to submit it. There is the Joomla! Extensions Directory for that.
If it does integrate with K2, please make sure your extension and/or template meets the following guidelines before you submit it to the K2 Extensions Directory:
1) Use only the name of the extension or template, e.g. you would use "Nuevvo Toreda" but you would NOT use "Nuevvo Toreda - Responsive eCommerce Joomla Template". Instead add tags for any attributes that differentiate your product. For this example, we would add: "responsive", "ecommerce" and "template". This makes filtering e.g. only for "responsive" templates an easy process for the site's visitors.
2) Make sure your presentation HTML is clean. Do not use inline links (they will be stripped off either way), tables or other weird HTML elements (span, font etc.). Only basic HTML formatting is allowed: strong, em, ul, li, img, h3, h4, p, div, br. DO NOT colorize phrases to make them stand out.
3) Use proper English in your presentation text. If English is not your native language, ask the help of a friend. Don't use Google Translate or other non-human translation services. Spell-check what you write. Make sure it makes sense. Use the universal typing and punctuation rules (e.g. one space after a full stop or comma, no double or triple spaces between words etc. etc.). Got lists to display? Don't use a hyphen. Make sure you use HTML to display them. Use the WYSIWYG editor for that. Entries that do not meet these standards will be rejected. If you're bored to check what you write, we are 10 times bored to do it for you.
4) If you need to add links, fill in the related Extra Fields section. Make sure you fill in as much as possible beyond the required.
5) Use at least 1 image (in the Image tab) to make sure your product is properly visible on both category listings and the presentation page. Got a video? Use the Video tab as well. Got an image gallery? There's the Image Gallery tab.
6) If you are offering a free product, you can choose to upload it inside the presentation page or use an external link. That's up to you to decide. But make sure you provide an easy way for people to download your product.
If you meet the above guidelines, your extension or template will be published within one week's time after it's been carefully moderated. If you fail to meet the above guidelines, incomplete entries will be permanently deleted after 2 weeks.
K2 brings the good parts from WordPress & Drupal into Joomla