I have searched youtube and google and everywhere but i can't find the answer to this question... I just got accepted into adsense so im new at it.. And i don't want to give my niche away so ill use an example. Say my blog is about baseball how do i get baseball ads on my site? Is there a way to do that? And i preferably want them to be pictures not just text.. Thank you VERY much if u can help me!

Google shall automatically determine the content of your website, and shall put the appropriate ads. You just have to put the adsense ad code in your website

You do not choose what ads will show up on your website.

Google will post relevant ads based on your site's content.

You can't select the topic of your ads, as the others stated above,
but...
you can select your preference for image ads instead of text - when you get the code for your ad, select "rich media" only.
I wouldnt do it, but if you want to you can...

i heard that google will recognize what your blogs are about after awhile and will eventually change...

Google shows ads based on relevancy so if your content is about baseball than it'll show ads in the category of baseball, but if there are no advertisers related to baseball than it will show a broader category, i.e. sports....it also depends on how well the advertisers write their ads (if it has the keyword "baseball" in it) and if their sites are relevant too.

Depending on the nature of your site you can also block certain advertisers and categories so their ads don't appear. For example, if your site is about baseball and you've noticed a bunch of Super Bowl ads appearing because of the big American football game next week, you could block the category football.

Make sure your blog's content has majority of it pertaining to baseball and also put the tags or label baseball related,. that way adsense would put ads pertaining to it.and if you do want a image ad, just customize it on the adsense code.

I would suggest you to go for contextual ads which would show relevant ads according to your website. You can use the Google Adsense for this.

There are also sites that you can sign up for where website owners are looking for adspace. but the problem is you have low traffic so not sure how effective this would be. I think you need to have a reasonable amount of traffic otherwise people wont be interested.

Maybe try and contact some related baseball sites direct to see if they are interested in a banner and negotiate a price.

we can not choose ads in google adsene,google self determine yr site content and putting adds