How to deal with large uploaded images

I’m designing my first minimalistic wordpress theme at the moment. It’s a simple 2 column layout (sidebar on right). I’m wondering how I should deal with users uploading large images which stretch out further than the content (which underlays the sidebar). Should I leave this up to the user to deal with, or apply a function to limit the image size?

Yep, I know how to restrict the size of images in wordpress, I’m wondering if it’s good practice to do it for a free theme for general release?

Don’t forget that you will often have to educate your clients about working with images. If they don’t have any image editing software I usually provide them with a list of software they could use, ranging from Freeware image resizing/cropping tools to full blown editors.

I don’t know if Wordpress does this, but CMS’s often come with a facility to check/limit the size/dimensions of an image on upload, if it’s too big the CMS will give them a warning and not allow them to upload anything larger than you specify.

I think it’s good practice to give your users both options.

As stated above, it’s important to educate your users, let them know there is a switch they can set to control image size.

I don’t see many themes being written this way, most publishers fill their themes with generic content or Latin text; Why not fill those pages with instructions on how to edit/personalize the theme?

Sorry, I 'm probably unclear with my question.
In relation to users displaying images with my theme, what is the best practice for theme designing? Allowing the user to place any size images (e.g. 1200px) or restrict image sizes to a max size?

Define width and height for img tag… or read this: to add custom sizes.