I wouldn't recommend putting an image inside a paragraph module or within a set of <p> tags because it will usually show up cut off in Outlook which uses the line-height of the paragraph to compute the display height for the image container.
The [FLEX] Email Framework is great because it makes this a bit easier to accomplish because there are controls built into the module that allow you to adjust the HTML and CSS without needing to know any code. Email code is one of those things where you really get what you pay for and this is an example of a situation where you'd want your development team to have some experience in Marketo with emails to make considerations for "future-proofing" rather than just building in the basics against a specific design.
To add padding to the left or right of the image really depends upon how the module and template are coded. This can be a real pain if you're not using something that's built to accommodate this kind of thing (and sometimes harder to fix in the context of your template code than it'd be to start from scratch). If you'd like some practical help here in the community it might be helpful to post the HTML for the module you're using and/or your template HTML so that the folks here can have a look and make some recommendations.
You should also have some different controls built into the module (in the right sidebar of the editor) as well as a display dialog box that pops up when you click the image (if it's using the mktoImg syntax) and you may or may not be able to edit the dimensions of the image there, but again it depends on how your template was setup in the first place.
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