If you need to save a rendered raster image of your Inventor part or assembly for further processing (e.g. for documentation, sales materials, advertisment), you don't need to obey limitations of the Inventor Studio renderings (max. 4096 pixels) - you can also use direct saving to a raster image file - to a BMP bitmap, and since version 11 also to GIF, JPG, PNG and TIFF file formats.
Choose Save as > Save Copy As > BMP (Save as BMP, PNG or TIFF), click the "Options" button and enter the desired resolution - at least 2000 pixels in both directions (maximum is 10000 pixels for both axes, i.e. 100 MPx). The resulting high resolution raster image file will have many megabytes, but it can be compressed well, or converted to other raster formats.
The image file will be saved in the current Inventor visual style.
Optionally you can save the image without background (just the model) and use the transparent background to merge it to the resulting scene in a DTP software.
You can also bring your model to 3ds Max to perform a hi-res rendering.