I have no clue about Android markets, but let me make some reasonable guesses.
First, concerning promotion: It's no rocket science to find appropriate place to promote your app. Just use Google, Bing, or blog search engines. For example 'Android AND app AND review' should give you some results for appropriate places to ask for a review. Another option would be 'Android AND app AND community' for places to post links.
A slightly more complicated way is this: Use the keywords most likely being used to find your application and look what the current results are. For example, the obvious keywords are 'Android AND Wallpaper OR Ringtone AND Download'. There are already about 3,490,000 results on that query, so check out the first pages. Try similar queries, too.
With a list of highest ranked pages, you can use a backlink tool to find out who links to those pages. These are the pages you're looking for. Since they already posted a link to sites discussing the topic, they are likely to post about your app, too. Just contact them in a reasonable manner (ie. no mass mails, etc.).
Second, getting people to download your application is slightly more complicated. For your app is free. This makes it easy to download and use, but there's also nothing that makes users do it now. In other words, they are likely to procastinate the download.
Under these circumstances, they only way to get them to act is building something really compelling. For example, if you have the largest collection of wallpapers and ringtones for Android, this may be good enough.
A better way is a (time) constricted offer: If there's something in your app that users would usually pay for, say the ringtones, you may offer some of them for free during a 2 weeks trial period. Such a restricted offer also makes it more likely that other sites will review your app and post about it. People want what's scarce, so make something in your app scarce.
Hope this helps.