Hi Kevin,
1 - For images I usually do something like this inside the .ascx file:
< % = ModulePath % > images/my-image.jpg
This will give you the correct path for images inside your module folder - (I have added extra spaces so that the forum editor doesn't break it)
2 - In regards to CSS or JS files I usually do something like this within the code:
protected void Page_PreRender(object sender, EventArgs e)
{
ClientResourceManager.RegisterStyleSheet(this.Page, base.ControlPath + "Resources/css/module.css", DotNetNuke.Web.Client.FileOrder.Css.DefaultPriority);
}
I hope this helps.
Cheers,
Aderson