I think that you’re just running into a wall if you want to transform a 2 dimensional picture into a full blown 3D sculpt.
What you could do instead of modelling a base that would look very roughly (no need of detail) like what the image is.
By example find a reference image and press N, enable "Background Image and load the reference.
Add a plane, go to Edit Mode , in Ortho view (Numpad 5 or View -> Orthographic) and go to the Right Side View (numpad3 or View -> Right)
Go to Wireframe display (or press Z) and start extruding roughly following the image as reference, don’t do the ear, stop at the head, you’ll see why later
Then select all and press E to extrude and give depth
Then select all, press W->Remove Double just in case and press CTRL+N to recalculate the normals that may have gone inverted due to Blender crappy normal generation on extrusion.
Press CTRL+R and add a central loop
Press CTRL+S -> Cursor to Selection to move the 3D Cursor at the center of that central loop
Go to Object mode and on the toolshelf (panel to the left) , at the Tools tab, click on the “Set Origin” button and select “Origin to 3D Cursor”.
Add a Subdivision Surface modifier, set it to level 2 (increase the View setting to 2) and click on Apply to apply the modifier, this is to give some geometry to work with in dyntopo sculpt more confortably
Go to sculpt mode and enable “Dynamic Topology” on the toolshelf , then start sculpting. With Symmetry enabled with X selected for the axis.
If you never sculpted, that’s going to be a good occasion to get some practice, play with the detail level (the less , the more detail it will create) etc.
Now for the part about the ears, i didn’t told you to model them on purpose just to show an usage of the dyntopo version of the Snake Hook brush that is interesting to make protuding bits.
First , give a bit of vertice density where you want the base of the ear to be (lower the detail to 5 or 6 hen use the Clay brush around it) .
Select the Mask Brush and paint the location
Now press CTRL+I to invert the mask , so everything is black, excepted the area where we’ll have the ears
Select the Snake Hook brush, set it a low detail (5 or a bit lower) and set the dyntopo to Subdivide Collapse if it’s not already setup to it.
Grab the unmasked area and move the mouse to give birth to the ears :
You can press ALT+M (or Mask -> Clear Mask) to clear the mask and start sculpting the ears now or keep the mask so you don’t give accidental brush strokes to the body.
After that it’s up to you to detail and sculpt your rabbit or whatever the creature is