Plagiarism?

There is an issue that I have been running into while doing homework assignments. Here it is: If I have an assignment that requires the creation of a poster or logo, etc., is it okay to use some things off of the internet? For example, if I have to make a logo for a made up amusement ride, and it is all my own creation but I use little designs like a decoration or another example is the design in the picture on my header. I chose the flowery design, but I changed the color and flipped them around and such. I understand I cannot fully say that this design is mine, but is it still okay for a homework assignment or is it considered plagiarism if I use it within my design? I think that is very confusing to decide what is plagiarism and what is not with design. I simply do not have time to create every little detail for a design right now, of course I will later for my portfolio to keep and use later.  Other than that, I really am improving week by week and I am becoming way more confident in myself. When I first enrolled for classes I was so nervous because I have no artistic skills at all really, but I can truly say I am happy with my progress. Except sometimes when I am running behind schedule for my homework assignments and have to half heartedly finish an assignment. But I think that my schooling is going great and I am very proud to say I am a student of Full Sail University.